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THE MOBILE TELEPHONE 

IN BELL SYSTEM SERVICE, 1946-1985

INTRODUCTION

The first car telephones were put into service in 1946, as a response to the growing mobility of the American population in the postwar years.  Initial design of the mobile telephone itself was undertaken by the Western Electric Corporation, the prime supplier of telephone sets to the nation's Bell System operating companies, while Bell Laboratories itself designed the overall system and set the specifications for the equipment.  At the same time, the independent telephone companies were developing their own equipment, to be supplied by Automatic Electric.  The Bell System equipment built upon an already existing mobile radio set, Western Electric's 1945 vintage Type 38 or 39 VHF FM police radio equipment, adding a telephone style handset and a selective calling decoder, which rang a bell in the automobile when that phone's unique number was signaled. The selective calling decoder consisted of a small wheel in a glass enclosure, with pins located at certain points around its circumference. The decoder had been developed in the 19th century for railway right-of-way signaling, was later used in ship to shore radio telephone installations in the 1930's, and was a proven concept.  This decoder was labeled "102." Western Electric and the Bell companies thus did not draw up an entirely new concept for a car telephone in 1946; they used proven components of other systems to create the new public car telephone service.

Mobile telephone equipment had already been in use internally within the Bell System on an experimental basis, going back before WWII,  using mobile radios such as the Western Electric Type 28 VHF equipment. One example was the Emergency Radiotelephone Service established by New York Telephone in December, 1940, which used AM on the 30-40 Megacycle band.  Based on the successful tests of that equipment, AT&T announced the creation of the General Mobile Radiotelephone Service on June 29, 1945, and applied to the FCC for authority to establish base stations in Baltimore, Chicago, Cincinnati, Milwaukee, Philadelphia, Pittsburgh, St. Louis, Washington DC, Columbus Ohio, Denver, Houston, New York City, and Salt Lake City.  One has to wonder why nothing was initially considered for California.

The FCC and the Bell companies envisioned two forms of mobile telephone service, "HIGHWAY" and "URBAN." Both would be VHF, and both would use FM. The "Highway" service, as its name implies, was intended primarily to serve the major land and water routes that existed across the United States in the 1940's, which would not be served by the "Urban" systems. Highway service was intended for trucks and barges on inland waterways rather than private vehicles.  Highway service was allocated 12 channels in the VHF "low band," with the mobile equipment receiving on 35 Megacycle and transmitting on 43 Megacycle frequencies, although not all 12 channels were initially used.  The Urban equipment, as its name implies, was intended to serve mobile subscribers whose travels took them primarily within the immediate radius of a major urban center, such as doctors, delivery trucks, ambulances, newspaper reporters and so forth.  Urban equipment operated on VHF 152 Megacycles (receive) and 158 Megacycles (transmit,) and the initial FCC allocation in 1946 was for 6 channels. The separation in transmit and receive channels was necessary to provide a "half duplex" communications circuit, and allowed the telephone company base station to remain on the air continuously during the duration of the call. The first Highway system went on the air in August 28, 1946 in Green Bay, Wisconsin, and the first Urban system went on the air in Saint Louis on June 17, 1946.

By 1948, Urban service was available in 60 cities in the United States and Canada, with 4000 mobile subscribers, handling 117,000 calls per month.  Highway service was in place in 85 cities with 1900 mobile subscribers, handling approximately 36,000 calls per month, with most major highways in the east and Midwest covered. 

The Bell System also entered the two-way business and police radio market after the war by offering the rental of entire radio systems including their maintenance and updating.  This equipment was marked "Bell System" either in white painted letters or with water-slide decals.  Smaller police departments were encouraged to use the "Urban" mobile telephone system as opposed to a traditional dispatch system, which must have been somewhat odd in operation.  Most of the equipment rented by the Bell System affiliates was Motorola two-piece "Deluxe" equipment, FMTRU-5V "Dispatcher" and GE one-piece pre-Progress Line radios.  It is believed that the Bell System discontinued this practice sometime in the early to mid 1950's.

ORIGINAL URBAN SIX CHANNEL ALPHA-DESIGNATORS:

WJ  WR  JL  JP  JR  JS

ORIGINAL HIGHWAY ALPHA CHANNEL DESIGNATORS:

ZF  ZH  ZM  ZO  ZB  ZA ZL

POST-NARROW BANDING ALPHA CHANNEL DESIGNATORS:

Highway:    ZO  ZF  ZH  ZM  ZA  ZY  ZR  ZB  ZW  ZL

Urban:       JL  YL  JP  YP  YJ  YK  JS  YS  YR  JK  JR

UHF:      QJ  QA  QP  QB  QR QF  QS  QH  QW  QL  QX  QM

Above post-narrow banding designators as of 1968

THE FIRST CAR TELEPHONES 1946-53

Typical installation of the first car telephone:

The Western Electric house-made equipment consisted of two pieces; the transmitter cabinet and the receiver cabinet. These mounted in the automobile trunk, and a large cable brought forward under the carpet connected to a "control head" under the dash which contained a telephone handset. The control head featured two illuminated lenses--one indicated that the equipment was turned on, and the other would illuminate when the mobile telephone was called. The Western Electric Type 38 was Highway band equipment, i.e. VHF low band, and the Type 39 equipment was Urban, or VHF high band equipment. A complete installation would be prefixed "2"; in other words, type 238 would be a complete Highway mobile telephone, and type 239 a complete Urban mobile telephone. As originally supplied, all equipment was single channel in operation.

The first mobile telephone control head was the Western Electric Type 41A, seen below. The handset, with a cloth braided cord, stores in a curious-looking spring loaded pocket on the bottom of the control head. The bell and terminal strips for cabling are self contained in the 41A.  There were two styles of 41A control head; the difference was only in the faceplate around the pilot lamps and toggle switch.  The 41A set was technically a single-channel installation although a multi-channel switch was developed which mounted alongside in a separate box.

The equipment for decoding a ringing signal to a particular car was the Western Electric 106A selector set, and in the type 38 and 39 receivers, it was mounted inside the chassis. Western Electric later manufactured a separate housing for this decoder, such that it could be used with other makes of mobile radio equipment, such as the Motorola "Deluxe" line two way FM radios and the GE 1949 "Pre Progress Line" two piece sets.

CLICK HERE FOR A PHOTO OF A TYPE 41A HEAD IN USE 

The decoders in these sets were capable of responding to a maximum of five digits, and operated by a series of small pins placed in holes around the circumference of a toothed ratchet wheel. As the operator dialed a specific mobile unit, all the wheels in all of the mobile phones within range would begin to move in step with the pulses being dialed from the telephone company's base station. At the end of the first digit, only those mobiles with pins in the wheels set to that number would hold the wheels at that spot. The others would reset to the rest position. This process would continue through the fifth digit, at which point (ideally) all the decoder wheels in the other mobile phones would have returned to the rest position except the one whose five pins matched the number dialed by the operator, at which point the wheel would close a switch and the mobile's bell would ring. The signals from the telephone company were audio tones, alternating between 600 and 1500 cycles as a digit was dialed.  It was possible to hear the stepper wheel operating in your trunk with calls for other people, and even to anticipate when your phone would ring by listening to the stepper ratcheting.  

This first system of mobile telephony would come to be referred to as "MTS." There were no dial facilities in the cars - - to initiate a call, the push-to-talk button would be depressed briefly, which would cause a lamp to light at the mobile operator's switchboard and put the base station at the telephone company on the air. The mobile unit would give the operator its telephone number and city of registry, and the desired number to be dialed. The mobiles were not "duplex," i.e. operation of the handset pushbutton was "push to talk," and "release to listen." The majority of the mobile telephones had no squelch circuit, so the characteristic FM "rushing" noise would emanate from the handset whenever the base station went off the air. This was not a problem since the handset audio was muted whenever it was hung up on its cradle.

Equipment manufactured by Motorola (the "Deluxe Line") was also placed in service together with the Western Electric, principally on the "Highway" channels, along with a small number of GE two-piece FM transmitter-receivers (also for "Highway" service.)

Independent telephone companies utilized equipment nearly identical to that of the first Western Electric car telephones, which was manufactured by Automatic Electric Co. as shown below, and believed to have been used with Motorola and GE radios:

:

The photo below shows a Motorola "Deluxe" line high band "Urban" radiotelephone installed in a taxicab in Delaware in 1948.  The rotary signaling selector unit is shown on the far right.

MTS CAR TELEPHONES OF THE 1950's

 THE NEXT GENERATION

By the early 1950's, Western Electric had dropped out of the mobile telephone and two way radio business, but the gap was quickly filled by a number of manufacturers including Motorola and General Electric. Mobile telephone service in the original operator-dialed, "Manual" system would later come to be referred to as simply "MTS". At this time, channels remained in the VHF low and high band assignments. There were no UHF Bell mobile telephones until the 1960's.

Mobile telephone channels, at least in urban areas, were already fully loaded by the end of the 1950's. Waiting lists for a mobile number grew in length, and subscribers often resorted to registering a mobile in another state just to get a number, using that number to place calls as a "roamer" in an area which had no new numbers available.   Statistics show that the Bell System companies had literally thousands of people on waiting lists to become customers, and had resorted to a somewhat "elitist" system of assigning new numbers, giving priority to doctors, hospitals, emergency crews and so forth.  Even so, I have to comment that "thousands" of potential customers does not mean that the American population as a whole was desperate for a mobile telephone or even saw the need for one.  The Bell System and the FCC were not "feverishly" working on a cellular mass-market system as assorted recently written web pages and revisionist college texts would like to portray the situation.

Although Western Electric no longer supplied the radio equipment, they continued to supply control heads and decoder-selectors with appropriate cabling to the Bell operating companies. The telephone companies would order the equipment through Western Electric, which would supply the equipment accompanied by Western Electric accessory sets.  Equipment seems to have also been ordered directly from GE or Motorola, supplied as a "KS-" numbered item rather than a Western Electric branded item, with the control heads and accessories still being purchased from Western Electric. 

A new design control head was introduced in the early 1950's, called the type 47, which was made at least through the model 47E series (1961). The main difference between suffixes seems to have been the type of handset.  While all 47's used the new "G" style telephone handset,  the earliest models have a heavier, bakelite version of that handset. The 47E has a built-in "transducer ringer", to be explained later, and a lighter weight plastic handset. The 47 series control head had such improvements as a key lock (standard) to prevent unauthorized use, and a smaller size with more flexible mounting arrangements than the type 41A.  However, the type 47 does not have either a bell or a terminal strip included inside, and therefore it was necessary to include a separate bell box with terminal strips, the Type VJB-1 bell and terminal strip housing.  Both the types 47 and 41 required external "outrigger" boxes to add multiple channel selectors.   Trivia:  The Type 47 key switches are individually keyed.  Technicians had a master key, to eliminate having to ask the customer for his key.  

The head below is a 47E series head from San Francisco.  It was probably used with a transistor-power supply GE Progress Line radio package, because of the "negative gnd." warning right on the ID tag.  There are colored lamps hiding under the paper tag; one for "ON" and the other for "CALL," which lit when a call was received.  The writing above the dot on the right is the mobile's number, and below the dot, "San Fran,"  the city of registry.  Since it is a 47E series, it probably dates from 1961-63.

The photo below shows the VJB-1 terminal and bell box.  There is a small bell inside, and this box was usually mounted in the front kick panel area or under the dash, where the bell could be heard.

Throughout the early 1950's, a typical MTS installation would consist of a nearly generic Motorola Deluxe, Research Line (later "Twin-V") or GE "Progress Line" two way radio with a Western Electric 41A or 47A series control head.  The Motorola equipment always used the Western Electric 102A external selector, whereas the GE Progress Line equipment used its own internal selector, labeled the VS-1.  Older GE equipment pre-dating the "Progress Line" also used the external selector.  Typical Motorola radio numbers were W43-1 and W41-1, the "W" standing for Western Electric contract, and the 43 referring to "Urban" while the "41" represented "Highway." Later Motorola numbers were typically  W43GGV-1 and W41GGV-1.  The GE post-1954 "Progress Line" equipment was numbered WA/E-33 or 36 and WA/E-13 or 16.  The GE Progress equipment initially came in 17" cases to accommodate the internal selector set and a multiple channel deck.  The transistorized power supply 12 volt GE "Progress Line" mobiles of the late 1950's had enough room inside to allow use of a narrower, and otherwise standard 13" case. 

CLICK HERE TO SEE A PHOTO OF A TYPE 47 HEAD IN USE IN 1960 

The example below is a vibrator powered 1956 vintage high band GE  Progress Line 17 inch "wide case" mobile which contains the internal VS-1 selector.  Trust me when I say this is one heavy item!  This normally would have fed a Type 47A control head with VJB-1 junction box and was capable of being wired for either 6 or 12 Volt cars.  The "Bell System" stencil on the case indicates that this was company-owned equipment.

Shown below is a Secode MTS head circa 1959 as used on a high band VHF GE transistor powered Progress Line MTS single channel telephone by an independent telephone company in the northeastern USA.  These systems were generally single channel and all were push-to-talk half duplex systems.

Photo courtesy Dalene Dutton

CLICK HERE TO SEE EXAMPLES OF MOBILE PHONE ANTENNAS OF THE 1950's 

TRANSITION MOBILE PHONES, 1958-67

Near the end of the 1950's, GE and Motorola began introducing mobile telephones with a few improvements over the original MTS phones of 1947. One of the improvements was the use of transistors in the radio power supply instead of vibrators and dynamotors, and miniature tubes with greatly decreased battery drain. Reliability went up as well. Another improvement was that the majority of mobile telephones being produced during this era had multiple channel capability. The 41A control head was discontinued by the mid 1950's, and new equipment was supplied with the 47A through 47E series control heads only. There were accessory boxes which contained a multiple channel switch for use with the type 47 control head.

The GE Progress Simultaneous Duplex (DTD/DTO/DTR)

By far the most revolutionary car telephone improvement of the late 1950's was the "duplexer", a radio frequency filter which allowed the transmitter of the VHF high band mobile telephones to go on the air while the receiver was still listening, using the same antenna. This operation is called "full duplex" and allows the subscriber to use the mobile telephone in much the same way he would a regular home telephone, since it was now possible to listen while talking.  GE was apparently the first manufacturer to introduce a duplexer into a conventional mobile telephone during this period; it was installed in the new "Simultaneous Duplex" series Progress Line mobiles, which also contained a new rotary selector of  Secode Corporation manufacture. The duplexer was a small rectangular can mounted on the front panel of the mobile radio. Although these mobiles were full duplex, it was still necessary to "push to talk" on the handset to put the transmitter on the air. Full duplex in these mobile radiotelephones simply meant the receiver would no longer be muted when the handset button was pushed. This equipment used the same receiver and transmitter as the earlier non-duplex equipment, although extra shielding was installed along with the duplexer.   Motorola equipment would not feature a duplexer until 1964's TLD-1000 series radio.  Some low volume manufacturers such as ITT Kellogg and AC-Delco also offered duplexers at the same time, so it's not exactly clear which manufacturer was technically first with this feature.

Simultaneous Duplex equipment came in three models:

DTD:  Operator dialed ( manual) no dial in head    DTO:  Mobiles may dial   DTR:  Mobile dials + identifies

The GE Simultaneous Duplex used a control head manufactured by GE, unique to their equipment. The handset hung up across the top of the housing, as on the older Western Electric 47A. This equipment could be obtained with up to five channels and was available for VHF only, although there is anecdotal evidence that a UHF version may have been made after 1963 in small quantities.  There was no "Highway" low band version, although there was a "simplex" configuration of the DTD style mobile which could be specially ordered with low band "strips" inside. The DTO/DTD could be configured with various options, such as "busy channel lockout" and "reverting". Reverting simply means that if a call was made on a non-home channel, the mobile would "revert" to listening on the home channel when the call was completed and the handset hung back up. This was done electromechanically using a solenoid interlinked with the channel selector mechanism. 

The DTO did not use a bell for a ringer; instead, a speaker was used to produce a high pitched audio tone. The limousine rear seat extension option consisted of a second control head, and a slightly modified control cable. The DTD or DTR prefix refers to equipment with the dial.  DTO is the equipment labeled "Manual" in the photo.  The DTR prefixed equipment is the same as DTO, the difference being that the rotary decoder was configured to "step by itself" to out-pulse the mobile's ID to the terminal so that no operator intervention was required at all.  With the DTO, on the other hand, while the subscriber could dial, the operator still had to come on the line to ask for the mobile's ID for billing purposes.  The DTR operated in close to the same way as the IMTS phones of the future would, except that there was no channel scan for marked idle or automatic channel selection, nor was the radio unit locked in the always-on transmit mode during a conversation.  Note that the DTD and DTR series telephones were rarely used by any Bell affiliates and were found more often in sales literature than in actual service.  Also note that there is some irregularity in the appearance of these heads.  The actual example of a DTO head below does not have the third "Busy" yellow lamp shown in the factory photos, and unlike the factory photos has a push-in switch added (apparently not standard since the escutcheon is not labeled as to its purpose) which activated the "AUX" feature (automobile's horn blows when a call is received.)

Typical DTD Series manual control head as used in San Jose, California on the Pacific Bell MTS system:

FOR MORE PHOTOS OF GE DTO SERIES EQUIPMENT, CLICK HERE 

The "Spark Plug"

Independent manufacturers began to surface during this period, although mobile telephones were still almost exclusively controlled by the Bell System (AT&T), owned by them, and leased to the subscriber at a rather outrageous monthly rate. One unusual independent manufacturer of a mobile telephone in 1960 was the AC Spark Plug Division of General Motors. Actually a Delco designed and manufactured radio, the AC Spark Plug "AChieverphone" saw service for a brief period of time in at least the Chicago and San Francisco/San Jose California areas. The AChieverphone used a proprietary 4-channel control head and cable rather than a Western Electric type. It had a transistorized power supply and a built-in selector which used a plastic decoder wheel. While compact, it did not represent any significantly new features or concepts in mobile telephony. Statements from General Motors at the time predicted that in "a few years" the mobile telephone would be standard equipment on all new cars. The AChieverphone was evidently their attempt to "get a foot in the door" of that future market. It was an idea about thirty years ahead of its time. There was apparently no rear seat extension option for limousines.  Another, apparently later, version featured a duplexer, but unfortunately my collection does not feature an example or any documentation on that model to provide here.

The ITT's

During this period, ITT, presumably via its ITT-Kellogg division near Chicago, made a number of MTS mobile phones which emulated Motorola products in features and components. Production of these mobile telephones appears to have stopped by 1964, and few have survived. Some of the various models were prefixed KH-. They are believed to have all been manual, vacuum tube models using Secode manufactured internal selectors, with the final model/s featuring a duplexer (but still MTS.) The radio package resembled a Motorola "T-Power" transistor-powered mobile.   Rear seat extension accessories are believed to have been available for limousines. The control heads resembled (or probably used components from) the Western Electric "Princess" or AE "Starlite" bedroom style telephones as was popular among the competition, and it is believed this model was referred to as the "Cinderella."

The Scantlin Selectors and the 47E Control Head

In the late 1950's, a Los Angeles area inventor named John Scantlin designed a transistorized mobile selector (tone decoder) to replace the now "venerable" Western Electric 102A mechanical stepper selector. Without any moving parts, the Scantlin SE-1315 selector was capable of more mobile number combinations than the old mechanical 102A, and therefore it was adopted by the Bell companies in the more populated urban areas where new numbers were needed. The control head used with the Scantlin selector was the Western Electric 47E. Rather than designing an entire new control head, Western Electric took the 47A series and modified it by placing a small hearing-aid type earphone into a machined hole in one end of the control head housing, which could be driven by an audio oscillator in the Scantlin selector, instead of the traditional mechanical bell ringer located in a separate junction box. The manual refers to this as "the transducer."  The Scantlin selector consisted of a number of small plug-in circuit cards, on a long rack, each containing a transistor and several other components. Technicians who serviced the units at the time have related that the Scantlins were somewhat temperamental and temperature sensitive, and were not well liked.

The Motorola MTS Radiotelephone

Motorola was not napping when GE came out with the DTO- series transistor powered Progress Line radiotelephone with built-in selector and duplexer, although GE's duplexer appears to have beaten Motorola to the market by several years. Motorola's choice was to introduce a completely new design, a thoroughly modern mobile telephone with built-in duplexer and solid state selector, about half the size of GE's DTO, and which was almost fully transistorized. Motorola's TLD-1000 series "MTS" mobile was marketed in July 1963, and drew heavily upon the design innovations featured in their "Motrac" line of conventional two-way radios. The only vacuum tubes used were the power amplifier and driver of the transmitter. There were no relays; all switching was done with transistors. The basic platform of the TLD1000 called for the capability to expand up to 11 channels, based upon the FCC decision in the early 1960's to "split" existing VHF channels and require "narrow band" 5 KHz deviation (versus the old "wide band" 15 KHz deviation standard in mobile systems).  The TLD-1000 was developed under the IMTS contract mentioned below, however it was initially sold as an MTS radio to be compatible with existing MTS systems, and to be upgraded later to full IMTS capability.  

The TLD-1000 used its own unique control head, with two rows of clear plastic pushbuttons to select the necessary channels. The basic, central portion of the control head can be seen to be a copy, in plastic, of the original Western Electric 47 series control head. This Motorola unit was fully accepted by Western Electric and usually will be found with an orange painted "WE" number stamped on the chassis, but was also assigned a "KS" number by Western Electric. The equipment could be configured for "battery saving", which involved splitting the power input wiring for the transmitter from the receiver. Unlike competitor's equipment, the Motorola set used the exact spacing of the transmit and receive frequencies, in MHz, as the receiver's IF frequency. In this way, it was only necessary to install one crystal per channel, which was used by both the transmitter and the receiver. In the TLD1000, the selector is mounted on a hinged bracket underneath the main chassis. A rear set extension control head was available for limousines. The "MTS" TLD1000 radio is essentially the same chassis as in Motorola's famous "MJ" TLD1100 radio, which is described later under "IMTS" equipment.

Note that the MTS control head shown in the brochure photo below was also sold with an external MTS decoder for use on conventional Motrac radio drawers, which were not duplex.  This setup was usually found on the low band "Z" channel equipment, which was never a duplex system, although some VHF MTS systems used conventional Motrac radio drawers as well, generally for telephone company owned vehicles and service crews.

There is an interesting example of the TLD-1000 head in use in the opening scenes of the James Bond film Live and Let Die where Bond is in the back seat of a CIA Chevrolet in New York and the driver takes a call (before being shot and losing control of the car.)  

PYE (ARC) Cambridge  (United States Communications) 

A rather obscure MTS Bell System mobile telephone was briefly imported by Aircraft Radio Corporation (ARC) which was actually made by the British PYE Radio company, as the Cambridge VHF FM radio.  This was a four channel set which made use of Ledex rotary relays for channel selection.  PYE (ARC?) foresaw the phone as being sold with an external decoder (MTS only, model not disclosed) and an Automatic Electric - Starlite / Princess style control head.  For some reason at least one mobile telephone service shop, United States Communications (Los Angeles, no relation to U.S. Communications of Idaho) chose to buy only the PYE radio drawer and manufactured their own heads and cable sets, using the Bell System Scantlin transistorized decoder and modified Automatic Electric "Starlite" telephones control heads.  The PYE set is very robust in terms of the case and mount construction, however the internal circuitry is unremarkable.  The ARC advertising flyer says that the rotary dial on the head performed some sort of function (there was no direct dialing in MTS systems) while the rotary dial on the United States Communications head was non-functional.

Click here for a pdf file of the above 2 page brochure.   1.6 Mb pdf file download. Be sure if printing that Adobe Reader is set for "fit to printable area."

Click here to see a great video clip from a "Mod Squad" episode showing this phone !

Other MTS Telephone Makes and Models Prior to 1964

There are no doubt a number of other makes and models of MTS mobile telephones not mentioned here. It is believed that Secode Corporation of San Francisco manufactured a mobile telephone in the approximate 1960 period, possibly relying on component modules supplied by existing mobile telephone manufacturers. Secode normally produced aftermarket selective calling and signaling equipment, and the electromechanical selector equipment for GE equipment through 1966. Other manufacturers included Industrial Radio Corp., International Systcoms of Canada, Mobile Communications Co. (Los Angeles) and the DuMont Corporation.  For almost the duration of Bell System mobile telephone service, independent dealers found such equipment very hard to get, and this situation drove the creation of some unusual phones such as the PYE/U.S. Communications "Cambridge" above and phones such as the Canyon and CSI equipment described later.  The independents could not purchase equipment direct from Motorola or GE and were forced to use refurbished items to a large extent.  At this time, they were in competition with the telephone company.  Any mobile telephone, even a used-refurbished one, sold for in excess of $ 1000, and the profit margin for independents could be substantial (unlike today, where the profit margin on a cell phone itself is well into the negative region, only the number itself representing value to the carrier and reseller.)

INDEPENDENT TELEPHONE COMPANY EQUIPMENT,

 1950-1970

While this web page is primarily concerned with Bell System equipment, the independent telephone companies such as GTE and Continental Telephone shared the same channels and often the same formats, and thus are worthy of mention.

These independent telephone companies, i.e. those not affiliated with the Bell System, offered mobile subscriber equipment not always the same as that used by the Bell affiliates, but which operated on the same channels and was generally compatible with Bell systems should the subscriber travel to a "foreign area" while "roaming." The independents should not be confused with RCC's, or Radio Common Carriers, which were privately owned firms, usually paging and answering service companies, operating on a different set of channels incompatible with Bell System equipment.. The largest independent telephone companies in the 1970's were Continental Telephone and GTE, but there were dozens of others including many rural telephone "co-ops."

"Dial" and "Identified Dial"

"Dial" was a system developed by the Secode Corporation in cooperation with GE to allow rural telephone exchanges owned by independent telephone companies to offer fully automatic direct-dial mobile telephone service to subscribers and Rural Radio Service (REA) users. The direct dial feature was not considered an improvement over the manual operator-assisted systems of the Bell companies, but rather was considered a necessity to avoid the need for salaried full time mobile operator switchboard staff and the significant expense which went with it. "Dial" systems were of two types: "Dial" and "Identified Dial."

The AT&T book National Mobile Telephone Service Area Listings, September 1974 edition, shows many independent and non-Bell telephone exchanges marked simply as "Dial."  Oddly, hardly any "Dial" or "Identified Dial" mobile telephones seem to have survived!

"Dial"

The "Dial" radio telephone was simply an MTS mobile telephone which was equipped with a tone oscillator circuit board which operated as follows: To initiate a call, the subscriber came off hook and listened to make sure the channel was free (some versions had a yellow "busy" light which would illuminate and usually block audio to the handset earpiece if the channel was in use). If the channel was free, the subscriber pressed a small button on the handset cradle. This sent out an "initiate" tone which brought the base station at the telephone company on the air. In some systems, the mobile subscriber then dialed the desired local number and the dial pulses were converted to interrupted tones sent by his mobile transmitter and translated back to dial pulses at the telephone central office. Long distance calls were diverted to a regular switchboard operator for toll ticketing.  The "Dial" configuration had no provision for mobile automatic identification, and subscribers were charged a flat monthly rate for local non-toll calls. Calls were generally limited by a timer at the central office. Signaling from the central office to a mobile used the same format as a conventional MTS radio telephone. A photo of a typical Dial mobile telephone is shown above in the GE "DTO/DTD" photos. It appears that Dial equipment was supplied exclusively by GE.

Identified Dial

Identified Dial is essentially the same as Dial, except that there was a provision to allow the electromechanical stepper-wheel of the MTS tone decoder (selector) to rotate on its own in order to generate a string of pulses representing the mobile's number. This was usually configured to occur when the "initiate" button mentioned above was depressed, after which the central office would decide if the mobile number was valid, and if so, a dial tone would be returned and the subscriber would dial the desired number. At the conclusion of the call, the subscriber hung up the handset, at which time the mobile unit would send out a "disconnect" tone signal, and the central office would disconnect the land circuit and return the system to idle operation (usually dropping the carrier at the central office transmitter.) Identified Dial is the system used by the GE Progress Line "DTR" Simultaneous Duplex phone mentioned above.  Otherwise, Identified Dial is unremarkable, except to say that it represented performance equivalent to the later-developed IMTS system, so long as automatic channel scanning was not needed (and providing the extra step of pressing the "initiate" button is not considered,) and so long as the mobile pressed the PTT bar in the handset when it was desired  to talk. The last identified dial mobile telephone manufactured is believed to have been the GE MASTR CC56 series duplex radio telephone, discontinued in the early 1970's. One example of Dial (possibly Identified Dial), would be the single channel mobile telephone system operated in southeastern California by Con-Tel (Boron/Mojave) in the late 1970's.  Identified Dial allowed automated toll ticketing as well as air time charges for every call, eliminating the need for operators on most calls.

Pushbutton Radiotelephone

Pushbutton was an interesting system proprietary to Motorola which first saw limited service in rural co-op exchanges and small independent telephone companies such as REA co-ops, which could not afford the overhead of a human operator to process and toll ticket calls.  It appears to have been manufactured from late 1957-1963 and competed with an Automatic Electric system in 1957-1958 for REA contracts.  These control heads were used both mobile or in homes (with a telephone-like handset cradle on the top.) Pushbutton is unrelated to Touch-Tone® or DTMF tone and was a proprietary dual tone system used only in this application. 

The Pushbutton Radiotelephone mobiles were not duplex, but push to talk, and consisted of regular Motorola "T-Power" and first generation "Motrac" equipment on one or two VHF high band channels.  Later versions of the Pushbutton Radiotelephone head had a cradle arrangement mounted directly across the front for handset mounting, with the key lock in that cradle and a two-channel switch where the key lock is shown in the version below.  Earlier versions hung the handset in a separate cradle elsewhere in the car dash area.  Interestingly, the pushbuttons stay depressed when dialing until the control head is finished sending that digit.  In other words, each digit is sent for a pre-determined period, over which the user has no control.  It must have been a bit disconcerting to dial this phone, when the head seemed to have a mind of its own.

The United States Government appears to have also purchased Pushbutton Dial equipment for use in their private exchanges, perhaps on large military bases.  The example shown below contains a "U.S. - AEC" property tag.

This phone had an interesting feature in later models, the "break-in" switch, which allowed a user to break into an already busy channel if he had an emergency.  This switch was on the rear of the control head, and when activated, sent out a tone to let the conversation on the channel know that someone was breaking in.   The black screw-in caps hold aircraft style "grain of wheat" lamp bulbs which illuminate the entire panel.

CLICK HERE FOR MOTOROLA BROCHURE PHOTO OF THIS HEAD WITH MOTRAC RADIO

(650 kb .jpg photos)

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IMTS and the Growth Years

 1964-74

On November 1, 1963, as part of the nationwide "narrow banding" of the two way radio spectrum, the FCC split the six MTS VHF mobile telephone channels into eleven, creating enough room (at the time) for more subscribers and newer design equipment.

Bell Laboratories had been slowly planning the expansion and growth of the mobile telephone industry for many years, and one development felt important in that regard was the need for automatic dialing from automobile subscribers and direct dialing to those mobiles from land based phones, and most importantly, channel trunking. Channel trunking refers to the ability of a mobile unit to search for an idle channel in order to initiate a call; this allows far greater loading of customers on a particular system than the old arrangement of a fixed number of subscribers "camping" on their particular "home" channel.

The solution was "IMTS", short for Improved Mobile Telephone Service. The development of the IMTS system was undertaken by the ITT-Kellogg Corporation, Secode Corporation, and Motorola, all of which received development contracts from Bell Laboratories.  A "test" IMTS system consisting of three channels was set up in Harrisburg, Pennsylvania,  in 1963, and used by mobiles registered to Bell System vehicles of the Bell Telephone Company of Pennsylvania.  This test system was demonstrated to telephone company executives from across the country, and also to representatives of the FCC, with the first installation of an IMTS system inaugurated in Charleston, West Virginia by November, 1964.  The equipment used was the Motorola TLD1000 basic chassis, mentioned with the MTS equipment above, upgraded to become the TLD-1100 equipment. This system, and the Motorola mobile telephones which operated in it, was called "MJ". Later, the Motorola TLD-1100 family of mobile telephone would be referred to by telephone company technicians as simply "the MJ radio." The Motorola MJ radiotelephone is easily one of the finest examples of American electronics technology, craftsmanship and quality, as well as one of the most complex.  The digital logic consisted of many Schmitt triggers, and was performed entirely with discrete components, no integrated circuits.  The circuit board was a three layer design.

How IMTS Works

All IMTS operation is full duplex, with the mobile transmitter normally on the air at all times during the call. Although designed for multiple channel operation, the realities of FCC licensing and competitive coverage areas meant that any MJ system would actually be limited to one or no more than a few channels, except in the largest metropolitan areas, where perhaps up to six channels could be assigned. IMTS operation requires a free channel to be "marked idle" by the transmission of a continuous 2000 Hz tone. The MJ mobile searches for that marked idle channel and locks onto it when found. If a call is initiated from the mobile, the mobile sends a brief 2150 Hz "guard" tone, followed by a brief 1633 Hz "connect" tone, followed by an 1800 Hz "seize" tone in response from the land station, followed by the mobile sending its ID in the form of alternating pulses of connect and guard tones, which make up the "ANI," which is how the mobile identifies itself to the telephone company terminal.  Initially, at least in some systems, the ANI was five digits long, and all mobile telephone numbers consisted of the alpha designation of the home channel, with the next five digits being the mobile number. This was a throwback to the old MTS manually connected system. A mobile number might be "JL5-2020, City of Registry, San Francisco."  Even though signaling was IMTS, these systems still operated in an MTS manner and required operator assistance.

Eventually, as the designers had intended, the MJ mobiles were re-assigned a normal seven digit telephone number, just as homes in America converted to "seven digit plus area code" telephone numbers from their old five digit system, to allow direct dialing without operator assistance. There was one major difference: in the mobile system, the prefix of the actual telephone number was never the first three digits of the mobile ANI and was not used to identify the mobile. The prefix, for mobile purposes, was ignored.  The mobile ANI consisted of the area code + the last four digits of the mobile telephone number. The digit series for the last four digits was then picked from a uniform list of digits reserved and wired to the mobile terminal in the area of the mobile's prefix..  For example, in Salinas, California, one of these series was 5000-5099, so that the mobiles using that terminal would all have numbers such as (408) 679-5030 or (408) 679-5099 with the mobiles actually set to signal 408- 5030 and 408-5099 respectively.  Mobiles in other prefix areas within the same area code were assigned from a different 100 digit reserved series.

After sending the ANI, the mobile unit would un-mute the earpiece and (ideally) the subscriber would hear a dial tone from the telephone company station, at which point the desired number could be dialed as on a conventional home telephone. When the conversation was completed, and the mobile "hung up," the MJ mobile would send a string of alternating "disconnect tones" before dropping its carrier and going off the air. The land station would then return to sending the "marked idle" tone. If the system was a large urban one, with multiple channels, presumably another channel would have already been marked idle, in which case the channel of the just-completed call would either drop carrier (not common) or begin sending a fast-busy signal (common).

The MJ Standard Control Head

The MJ system employed a standard control head design, all of which were manufactured by ITT and then labeled with the appropriate manufacturer's logo, such as Motorola, GE, Bell System,  left blank, or with a generic logo saying "Radio Telephone" (see example below.)  The control head is interchangeable among all manufacturers of the equipment, even though the actual electronics packages differ greatly.  The cables for the assorted brands of "MJ" equipment are also all interchangeable, so that a GE head and cable will work perfectly on a Motorola RF package, and vice versa.

GE also produced its own version of a control head for use in the MJ system, as shown in the GE IMTS section below.

The MJ head is probably the most recognizable mobile telephone head of the 1965-1980 period and can be seen in many TV shows of the era (such as Banacek, Hawaii Five-O, Ironside, etc.)

The example below is a standard MJ control head from a phone registered in California's Pacific Bell system.  The "revertive call" version would have had a "P" button for "party" in place of the "Aux" button.  See the revertive call description below.  

These heads were available in many colors.  The most rare is probably the pink one.  I occasionally wonder who ordered the pink head, what she looked like, and what kind of car it was in (Cadillac presumably.)

Typical colors ordered were black, white (subject to yellowing today,) beige, gray, Bell Telephone green, red (rare,) powder blue and pink.

The Motorola MJ IMTS Radio

The MJ radiotelephone is a standard TLD1000 MTS radio, but with a change to the selective call decoder assembly. In the TLD1000, this was a simple MTS decoder only, located on a hinged bracket underneath the radio chassis. In the MJ TLD-1100 radio, the decoder was part of a "supervisory package" located in a large swing-out chassis consisting of several circuit boards located above the radio chassis. The MJ supervisory chassis consists of the circuitry needed to scan channels seeking the marked-idle tone, outbound dial signaling, initiate and hang-up sequences, and automatic mobile identification. All MJ supervisory chassis also have full MTS signaling capabilities for manual system use. A few MJ "type" supervisory chassis were supplied with a proprietary Secode interrupted 2800 Hz tone signaling format for the "Manual" mode instead of the Bell System's standard  MTS tones.

The MJ was by far the most popular and common mobile telephone, made by the thousands. A TLD-1000 MTS radio could be converted to an MJ radio by replacing the supervisory selector chassis and the control head, although this did not seem to occur often.  Both the TLD-1000 and the TLD-1100 offered limousine rear-seat extension phones. The TLD-1000 MTS rear seat extension was a compact, attractive plastic unit resembling the older 47E series MTS control heads, but did not feature the ability to change channels. The IMTS rear seat extension was a rather crude and ugly-looking affair which evidently was pasted together in a great hurry, and few were sold. The IMTS rear seat extension allowed dialing but not home/roam/manual selection or channel selection.

The TLD-1220 was a TLD-1100 IMTS mobile which offered "revertive call" operation. Instead of the "Aux" button on the control head (which blew the car horn when the phone rang), there was a "P" button in its place. The "P" button stood for "Party" (party line), also called "Revertive" operation. The purpose of revertive call operation was to allow two mobile telephones to converse with each other on the same channel (push-to-talk operation only !)  Pressing the "P" button would take the mobile transmitter off the air and put it into push-talk operation via the button on the handset (in IMTS operation, the transmitter normally stays on the air continuously during the duration of the call.) When one mobile called another in a "revertive" system, the answering mobile would hear a special tone sent out by the central office (usually a string of "beeps"), or in some cases a recorded announcement saying to "press your "P" button;" the tones or announcement also being heard by the calling mobile such that both could comply. The central office station then acted as a conventional "repeater."  The TLD-1100 units had no way of receiving a revertive call, although pressing the "M" (manual) button would bring the radio out of IMTS mode and into manual, allowing the call to proceed, but at the end of the call, the mobile would be unable to then  send a disconnect tone in IMTS format, and it would be necessary to rely on the terminal to "time out" from the time the land party hung up, or from when the last carrier on the mobile input was heard, whichever occurred first.  Most independent telephone company units seem to have been TLD-1220's, while most Bell System units were TLD-1100's.

The GE MASTR CC56 IMTS Radio:

GE introduced an IMTS radiotelephone sometime in the late 1960's which provided the same features as Motorola's TLD-1100/1220 series, however in a somewhat cruder presentation with far greater size and weight. The CC56 was essentially a conventional 30 Watt MASTR Professional series mobile radio, except with the power supply mounted across the rear apron and a mobile selector - RF oscillator chassis in the center. The CC56 unit could be purchased with either an MTS/IMTS selector package (as the Motorola MJ radio,)  a "Dial" selector unit, compatible with the "Dial" and "Identified Dial" systems already in use with GE Progress Line DTD series equipment, or only an MTS decoder. 

The CC56 in the IMTS version could be supplied either with an "MJ" control head as used in the Motorola equipment, or a GE proprietary head (see photo below.) The GE CC56 was discontinued sometime in the mid 1970's, and was replaced with the MASTR Executive II equipment.

Note that on the "Dial" head shown below, there is an "Initiate" button on top directly in front of the control head.  Additionally, there was a sticker over the "General Electric" logo placed there by the telephone company giving instructions on how to place a call. Remember that "Dial" is not IMTS !                       

GE MTS EQUIPMENT

GE also continued to market simplex MTS equipment for both the low-band "Z" channels and the VHF high-band systems which were still MTS, far past the introduction of IMTS and through at least 1974.  The equipment used in both cases was a standard MASTR Professional mobile radio with a decoder added across the rear apron, and is otherwise unremarkable.  Apparently this was a lower cost option for MTS than the full duplex (in high-band only) CC56 series mobile radio.

OTHER MAKES OF MTS EQUIPMENT

As mentioned above, even though IMTS equipment was available since 1965, most telephone companies throughout the 1970's remained manual-MTS systems.  As a result, smaller firms continued to manufacture MTS car telephones, probably primarily for the California market, usually using used-refurbished RF drawers by GE, Motorola and others but adding control heads and digital decoders of their own design and manufacture.  Some of these are shown below.

CANYON:  Canyon Communications, of the Los Angeles area, was most famous for its manufacture of attaché phones but also made the RF sections of its attaché phones available as conventional mobile units ( MTS) in the late 1960's and early 1970's.  There were several models, one of which curiously had the RF channel oscillators built inside the control head as shown below.  The construction quality and appearance of these Canyon units appears a bit crude.  It's easy to recognize that the head below started life as a Western Electric Trimline®  wall phone. 

Canyon also manufactured a radio package which apparently never came with a control head of their own manufacture.  Labeled Mark 900, the same as their attaché phones (see below,) this was rather confusing.  Customers were evidently expected to use a Secode or (later) Glenayre or Harris head with it.  There was no logic inside the unit itself.

Click here for interior view of the above MK900 chassis

CSI :  Communications Signaling Inc. was a Los Angeles used-equipment refurbisher which sold mainly Motorola and GE radio packages, some with new control heads of their own construction for MTS use, in the years before IMTS became standard.  In the 1980's, they also sold these radios with Glenayre IMTS control heads as IMTS mobile telephones.  They seem to have gone out of business in the early 1990's.   The head below is labeled CSI 209 and was supplied connected to a GE CC56 radio package in which the original IMTS supervisory logic had been removed.  It was sold under the model name "Superior" and could be had in sixteen different colors!  There were two buttons on the handset - - one is the push-to-talk while the other is the channel advance function.  The pushbutton caps may not have been black as originally shipped.  The decoder circuitry is built into the control head along with a small buzzer.  Another example is shown with the International Systcoms mobile telephone shown below. When this control head is in the "scan" mode, the light pattern on the channel lamps is fascinating to watch.

INTERNATIONAL SYSTCOMS:  Systcoms was a Canadian company later absorbed by Novatel in the 1980's. See the Systcoms information farther down in the 1974-83 category.

The Systcoms Century radio package in the photo below originally came with a 13 channel Canadian MTS control head in the early 1970's or late 1960's.  Here, it has been modified in approximately the mid or late 1970's to use a CSI scanning MTS head, built into an Automatic Electric Starlite telephone housing.  The various channel lamps illuminate as the unit is scanning and stop on channels which are available, per settings by the user.  The control and signaling logic is entirely contained within the control head, via a set of rather crudely made circuit boards and pin-jack fields. The transceiver is duplex.  This would have been usable in the California Pacific Telephone system up until the 1982 switch to IMTS, or in other areas which were still manual, MTS format (a surprising number of companies only converted to IMTS near the very end of this technology.)

LIVERMORE DATA:  Livermore Data Systems of Livermore, California acquired the rights to a mobile and/or attaché phone made by S/C/M Melabs (see below) in 1970 and began production in that year with the LAP-1000A Attaché phone. They had already been engaged in production of computer modems and related items since the 1960's.  Their first product was the Envoy 150, an MTS telephone sold primarily as an RCC item.  The Envoy 150 was rapidly discontinued and the same item became the "Satellite Channel Search Car Telephone," Model LCP-1010A.  The RF package of this telephone looked identical to the later "Satellite" phones as shown below.  The control head was a Secode VP-1 style head, which in appearance is the same as the "MJ" ITT control head shown above except that there is a blank plate where the dial would be.  See the Livermore Data category below for more information about this company.

SYMETRICS:  Symetrics of Satellite Beach, Florida was a small manufacturer which was making an IMTS mobile telephone by 1970, but little information is available.  The photo below has been blown-up from their ad in a 1970 issue of Communications magazine.  Note that the head must have been mounted as a prop in the photo, a Camaro interior, because the gearshift looks like it would have had a hard time reaching PARK with that head in that position!   Symetrics manufactured two mobile phone versions, the MTS-11 and the IMTS-11, at least through 1976.  As the model numbers imply, the MTS-11 was an MTS manual phone while the IMTS-11 was the IMTS version.  Power outputs were 20 Watts and there was no UHF version.

CLICK HERE TO VIEW THE FULL AD FOR THE PHONE ABOVE

S/C/M - Melabs:  Melabs, a division of Smith Corona, the typewriter manufacturer, developed an attaché phone design in 1970 that reportedly was later taken over, bought or copied by Livermore Data (see Livermore Data information below.)  Apparently due to some sort of lawsuit involving AT&T, Melabs sold the design and some tooling and inventory to Livermore Data Corporation.  The physical appearance of the Melabs phone is very similar to the Livermore version.   Melabs may have produced a mobile version which was the predecessor of the Livermore Data models, but information is lacking on this point.

CLICK HERE TO VIEW A 1970 AD FOR THE S/C/M MELABS ATTACHÉ PHONE 

INDUSTRIAL RADIO:  Industrial Radio of Chicago was primarily known for its manufacture of portable two way "pack set" and "field phone" police radios.  In approximately 1965 they marketed the "Aristocrat," a duplex  MTS telephone using an Automatic Electric dial "Starlite" telephone as the control head, which was actually just the older ITT "Cinderella" phone mentioned above.  Evidently ITT sold the rights to the phone when it exited the car telephone business, and there is evidence that Industrial was the actual manufacturer of the ITT Kellogg branded phones in the first place.   In 1965, IMTS had already been introduced, technically making the Aristocrat obsolete, although most areas of the country remained MTS throughout the 1960's if not well into the 1970's. California, in fact, did not convert to IMTS until 1982!  Industrial Radio had disappeared by approximately 1967.

1968: UHF Introduced, The Motorola MK IMTS Radio

In 1968, a number of UHF IMTS systems went on the air in urban areas. There were already a number of manual MTS UHF systems in operation in the larger urban areas as well, which had been placed in service in the early 1960's to relieve congestion on the VHF channels.  Motorola was already producing a fully solid state 12 channel UHF mobile radio called the MK XII (Mark 12), sometimes called the Motran Mark 12, which, with some modifications, became the T-1414 Duplex "MK" UHF radio. The MK system was merely a UHF IMTS format identical to the VHF IMTS system except that there was no manual operation capability. The system was fully automatic, direct dialing without operator assistance. The MK radio came with the "MK" control head. The MK control head eliminated the channel selection buttons and the "Manual" push-to-talk mode, but otherwise provided the same features as the MJ equipment. The MK radiotelephone used the same supervisory signaling package as the TLD-1100 "MJ" sets.  Roaming was available but via an internally strapped jumper matrix, programmed ahead of time.  The user could not change the Roam channel list himself.

At some point during production of the MK control heads, an optional "add-on" top section was added which allowed user selection of Roam and (apparently) Manual channels, although there would have been some difficulty using it in a "manual" system unless the handset was replaced with a push-to-talk model as well.  These pieces are rare and apparently did not see widespread use other than in large metro areas such as New York City and Chicago.

Photo courtesy of Steven Scher, Bronx NY

Like the TLD1100 "MJ" equipment, the "MK" equipment used no moving parts (i.e. relays or stepper switches). The supervisory board assembly is the same as in the TLD-1100 and TLD-1220 "MJ" mobiles. The MK receiver was surprisingly sensitive for its day, and the transmitter matched the power output generally available from VHF radios, doing so via a varactor tripler which required delicate and extensive filtering and tuning  in the transmitter output stage. The original MK equipment was replaced in the late 1970's by the "UHF Pulsar" radio drawer which would later be referred to as "Pulsar II" equipment.  The MK has a rather peculiar,  complex and expensive to make housing and tray assembly.  The example above is a former test unit from AT&T Labs in New Jersey.

MOBILE TELEPHONES 1974-83

These years represent the most prolific period of conventional mobile telephone history. There were many different makes and models produced; what is shown below represents only some of the more popular equipment.

MOTOROLA MTS EQUIPMENT

Motorola still manufactured MTS equipment well into the 1970's, but did so only to accommodate companies which were still using MTS systems, primarily those using the low band 35/43 MHz "Z" channels (which never went to IMTS.) These MTS radios were essentially traditional push-to-talk 2-way mobile radio chassis with an external decoder and a mobile telephone style control head.  These telephones replaced the earlier "Motrac" and "Motran" radio packages which were sold with the "Manual" mobile telephone style head marketed with the TLD-1000 MTS radiotelephone.

Below is a photo of a Motorola head used by Pacific Telephone with a 35/43 MHz special production "Micor" radio, from 1974. Only two channels were installed, ZM and ZY.  The other two pushbuttons were blocked from operating.  This was the last product Motorola manufactured for manual mobile telephone use.  It is believed that most of the subscribers on Pacific Telephone's Z Channel low band systemby the 1970's  were telephone company personnel.  You can see that the head is actually an "MK" rotary dial head modified with a plate over the dial cutout, which blanks the dial area and provides the channel-change pushbuttons and lamps.

The control head above was used with the following 4-channel Micor radio drawers, although it is believed that the majority of those sold were low band 35/43 MHz equipment.

The Micor radio drawers were numbered as follows:

Q1358:   55W   35/43 MHz ,       Q1359:   60W   152/157 MHz ,        Q1379:    45W   450 MHz  

The Q1358 was not duplexed - - presumably the other two were not either.

Motorola also marketed Q- prefixed Micor equipment with a duplexer as a UHF medical system ambulance radio, usually used in the "HEAR" ambulance radio system.

MOTOROLA 1970's IMTS EQUIPMENT

MOTOROLA PULSAR I:

In approximately 1971, Motorola introduced a new fully solid state VHF IMTS telephone called the "Pulsar," which replaced the 1963 vintage TLD-1100 and TLD-1220 "MJ" sets.  The Pulsar was built in a housing which appears similar to the conventional Mocom 70 style radio, but otherwise shared none of the aspects of the Mocom 70. The Pulsar used plug-in circuit cards in a "cage" and modules for all functions except the transmitter power amplifier. The Pulsar supervisory card made first use of a proprietary thick film hybrid IC. The duplexer was combined with the receiver front end circuitry, and called a "Trisolector." The Pulsar would be retroactively called the "Pulsar I" when the "Pulsar II" was introduced. The Pulsar was available with a variety of different control heads and options. It could be ordered to use the traditional control head of the earlier MJ sets, the "Pulsar" control head (a slightly smaller version of the MJ,) and the "FACTS" control head. 

Later, it could be retrofitted to use the Pulsar II series control heads as well as the Pulsar 100 and 120 heads.  The original Pulsar head did not offer interlocking "Roam" channel pushbuttons and was in that respect more cumbersome to use, at least in the aspect of a roamer trying to step through the various channels to find a marked idle tone. The "FACTS" control head deleted the "Roam" row of pushbuttons altogether and was essentially an IMTS control head designed for limited roaming through urban areas. It required a number of jumpers to be pre-programmed for the "Roam" list. The FACTS control head could also be used with the earlier "MJ" TLD-1100 series radios.  See below.

The typical Pulsar I model was T1878A or T1878B. Pulsars suffered from a number of reliability issues; these included poor contact between the sockets and the plug-in circuit cards, and burned-open foil traces on the mother board because they were unable to reliably carry the 10-12 amps of current to the final amplifier section of the transmitter. Otherwise, the Pulsars were a design rather ahead of its time.  Like the TLD-1100 "MJ" radios, the mobile subscriber's ID was programmed into the equipment by means of pin and jack connections on the supervisory printed circuit board.  When the successor Pulsar II was introduced, the original Pulsar could be retrofitted with the "MACS" option, which allowed it to search for and seize a vacant channel when a call was attempted during an "all channels busy" situation. "MACS" stands for Motorola Automatic Channel Sentry. This was an important feature in the days when waiting for a free channel could be a lengthy process, and allowed its user to "jump" onto a vacant channel usually before others, whose recourse was only to endlessly bring the handset off-hook looking for the green light instead of the red busy light.

The photo below shows a Western Electric marked Pulsar I on the left, and a Bell System marked Pulsar I on the right, with a MACS board installed above the Trisolector.   Note that they look surprisingly similar to Motorola's Mocom 70 line of conventional radios, yet they share nothing in common.  Even the housings do not interchange.

MOTOROLA FACTS:   

FACTS was not actually a new model of car telephone but rather simply a streamlined control head, as mentioned above, without the manual mode channel selector buttons of previous heads.  It actually slightly pre-dates 1974 and the FACTS heads can replace the standard MJ heads on all equipment (Pulsar sets required different interface boards for FACTS.)  The FACTS control head has what looks like an LED channel indicator display, but it is really a matrix of small grain of wheat lamp bulbs in a metal mask assembly.   One or two of these lamps are usually burned out, too.  "FACTS" stood for Fully Automatic Car Telephone System.  The FACTS head is very similar in operation to the MK head shown above, except that there is the illuminated channel display and provision for Manual, PTT style operation is retained.

[PHOTO TO FOLLOW]

MOTOROLA PULSAR II:

In approximately 1979, Motorola introduced the Pulsar II, their last IMTS platform.  Interestingly, the Pulsar II radio is much larger than the Pulsar I, much heavier, and more cumbersome to service. The Pulsar II uses a unique heavy, cast one-piece housing which was not shared by any other Motorola product. Pulsar II's continued the design of plug-in cards for the circuitry, but they were not interchangeable with the cards of the Pulsar I.  

The Pulsar II introduced some unique new features such as VSP (Vehicular Speaker Phone) and MACS (Motorola Automatic Channel Sentry, see above.)  The MACS board was also available as a retrofit option for earlier Pulsar I drawers, and in those sets was placed on top of the Trisolector casting (see photo above.) . The Pulsar II was first sold as a UHF version of the Pulsar I, intended to replace the MK mobile radio, and sold with either a UHF marked Pulsar I control head or an MK control head, and shortly thereafter was changed to use the Pulsar II style head shown below.  Then, a VHF version was produced, and Pulsar I production dropped altogether. This led to the early confusion of calling the Pulsar II the "UHF radio telephone" and the Pulsar I the "Pulsar radio telephone."

[Pulsar II radio drawer photo to follow]

MOTOROLA PULSAR 100 and PULSAR 120:

The Pulsar 100 and 120 control heads appear to have been cheaper alternatives to the Pulsar II control head.  With mechanical manual channel switch selection and rotary dial (100) or pushbutton dial (120) these heads offered "no frills" operation with the basic Pulsar II chassis.  They had no memory, no speaker phone and no digital displays.  These heads were widely used by Bell operating companies such as Pacific Telephone.  The escutcheons were available in either vertical or horizontal orientation to allow for mounting in various vehicle configurations.  The vertical format was usually used in cars with a solid center console.

GE 1970's IMTS Equipment

MASTR Executive II Mobile Telephones:

The GE MASTR Executive II mobile telephones were essentially a standard Executive II mobile radio with a duplexer (Phelps Dodge) mounted in a humped top cover section, and replaced the older CC56 series MASTR Professional series. They were also GE's last IMTS car telephone and available in both VHF and UHF.  Unlike the previous CC56 MASTR series, supervisory signaling equipment was not located inside the drawer itself but was expected to be provided by the control head, obtained separately. There were two Exec II versions, a synthesized version (prefixed CS56) and an older crystal control version (still prefixed CC56). Although there was an IMTS (Secode VP-5) control head offered by GE, most of these units seem to have been sold less accessories. Many of these units in VHF were purchased by Pacific Telephone & Telegraph in California around 1982, and used with a Callmaster MT-300 series control head.  In other areas, these drawers were used with the Secode VP-5 control head labeled "GE." See photo below.

OTHER MAKES AND TYPES OF EQUIPMENT 1974-1983

Attaché Case Telephones

Note-See also the attaché phones listed above prior to 1974

The attaché case telephone was very much a "James Bond" item offered initially  in the late 1960's, despite being somewhat impractical. Some of the makers of attaché phones were Livermore Data Systems Corp. of Livermore, California, Canyon Communications of Newhall California, GCS (successor to Canyon,) S/C/M Melabs, International Systcoms of Canada and one or two others. Most of the attaché case telephones were MTS, although Livermore and Canyon offered full IMTS/MTS versions of advanced design by the mid or late 1970's. The attaché case phones were very heavy and offered limited battery life. They were actually a mobile unit with a large nicad battery, all crammed into an attaché case. The antenna was a foil strip glued behind the leather interior trim of the upper half of the case. Jacks were available for external antennas and power sources, and in the case of the Canyon equipment, the briefcase telephone could be put into a vehicle trunk and a regular Canyon under-dash IMTS or MTS control head used with it by plugging the case into an extension cable in the car trunk. 

The Canyon telephones are the crudest in appearance and appear almost home-made internally. The Canyon service manual is full of hand-drawn schematics and hand-written notes, as if the item was created in someone's garage (it may well have been.)  They were obviously made in limited numbers and never benefited from the refinement of mass production. Construction and component quality are poor, and the circuitry amateurish in appearance. The pushbuttons are a cheap and unreliable design.  The later (after about 1977) IMTS Canyon briefcase telephones feature supervisory selectors supplied by Uniden of Japan. Canyon was absorbed or merged into GCS (General Communication Systems), which continued to briefly market an improved version of the Mark 900 briefcase phone, called the Mark 1000, in the mid 1980's. See advertisement below. 

The Livermore Data briefcase telephones were of much better quality than the Canyon products but are otherwise unremarkable, except that most of them when found today, other than having dead batteries, would still work.  The Livermore sets were initially MTS only in operation (LAP-1000 ?), but at least one full IMTS/MTS version was made (LAP-2000.) Livermore purchased the attaché phone assets from S/C/M Melabs, one of the first manufacturers of an attaché phone. Apparently the original attaché phone was called the "Carry Phone" and was designed by Melabs for S/C/M, however there was some sort of litigation with AT&T and Melabs abandoned the project after manufacturing a small number of phones.  Livermore Data Systems was also engaged in manufacturing acoustic computer modems and early computer items.  It later changed its name to Livermore Communications, when the data division was sold, and Livermore Communications went out of business in the early 1980's.  It is my understanding that one of the principals of the firm, Gilbert Margouth, was the mayor of Livermore, California and deputy California Superintendent of Schools at one time.

Both the Canyon and Livermore sets were high power units, approximately 20 watts, and battery life in IMTS operation was quite short. 

GCS MARK 1000 ATTACHÉ PHONE

LIVERMORE DATA LAP-2000 ATTACHÉ PHONE

Note the unusual hole in the panel where a switch can select 5 or 7 digit ANI's.  Apparently this was to accommodate areas still using 5 digit MTS signaling but also allowing roaming into areas with 7 digit IMTS systems.  This is the only phone I have ever seen with a customer accessible ANI switch.  

CANYON MK900 ATTACHÉ PHONE 

The Canyon Mark 900 was also available as a conventional mobile telephone (shown some paragraphs above under Canyon heading,) and this attaché case could also be placed in the vehicle's trunk and connected to a cable set, which would bring in an external antenna line and a control cable from the car's interior, where a separate control head would be mounted.  In other words, it became a conventional mobile telephone while driving, but when the driver left the car, he could remove the attaché case from the trunk and take the telephone with him.  There was a dummy plug which had to be replaced in the connector at the bottom of the attaché phone to return it to normal operation. 

The design of the Mark 900 began in 1970 and underwent a number of minor changes to the RF section and major revisions to the logic section during its lifespan.  It was also sold as the Skytronics Travtel in the early years of production.  Most of its production seems to have occurred in the mid to late 1970's, hence its placement in this section of the page.

The Mark 900 head, used solely on the attaché case, and not the mobile radio also called Mark 900, is shown below.

The lettering on the illuminated lenses was rather crude and poorly applied, and has flaked off over the years.

Apparently a final version of the Mark 900 control head:

TEL-COM 150A:

The Tel-Com 150 was manufactured in Garland, Texas by Integrated Systems Technology.  The 150A was manufactured in the early 1970's and about 2100 were made, at a retail price of $ 3500.  Appearance is practically identical to the Canyon MK900 shown above.  It is unknown whether any other Tel-Com attaché phone models were made.  Tel-Com sold a number of these phones to celebrities of the era and wealthy oil men, but otherwise, they are somewhat obscure. IST also manufactured a companion mobile telephone, and an accessory generic IMTS control head (see below.)

Photo courtesy Ron Smith   

TRIGILD:

A rather obscure attaché phone from Canada is the Trigild Gemini as shown below. It covers 13 VHF channels, the Canadian scheme, and is somewhat crude in presentation and appears to have not been marketed much in the USA, if at all.

Photo courtesy of Wikipedia

Mobile Equipment

LIVERMORE DATA SYSTEMS CORP. (LDS):

The Livermore Data Systems Company of Livermore, California, mentioned above, in addition to attaché phones,  made a variety of MTS and IMTS mobile telephones from about 1970-1984. Their first product was the LCP-1010 "Satellite Channel Search Car Telephone" (see Livermore, above,) a simple duplex MTS-only mobile using a Secode MJ-look-alike control head (Mark I) with the dial area blanked off, which was probably targeted to the California market (which remained MTS until 1982 !). 

Livermore's next mobile product was the LCP-2020 "Satellite", an attractive MTS/IMTS mobile telephone which used a modified Automatic Electric "Starlight" telephone as a control head.  This head is shown with a rotary dial as the Satellite IV and with a touch-pad dial as the Satellite V.  It is believed that few, if any, Satellite V's were made.  The Satellite IV as shown below had illuminated channel indicators under the front of the control unit and a small DIP switch for selecting the "Roam" list. Channel searching in progress could then be seen on the illuminated display. It used a standard "MJ" car telephone cable, which is universal among GE and Motorola made car telephones as well.  The radio package was basically the original MTS style LCP-1010, but with a new logic package. The 2020 was a reliable unit of quite pleasant appearance, although the control head was susceptible to RF interference from the unit's antenna in convertible cars.  Possibly my favorite car telephone in terms of appearance.  The 2020 was also packaged into an attaché case, more or less, at the same time, to create the Livermore Data attaché phone shown above.  The Satellite was made in two models - - LCP 2020, a 30 Watt unit, and the LCP 2020A, a 50 Watt unit.  Satellite production began in 1975 and continued through late 1979, when it was replaced by the Satellite 80.

Livermore Data "Satellite IV" IMTS Control Head, 1975-1979

The 2020 "Satellite" was followed by the 2080 "Satellite 80" IMTS VHF telephone, which was similar in appearance except that the control head was pushbutton (not DTMF !) and the radio package used somewhat modernized supervisory logic. The 2080 mobile control head was a maintenance headache, caused by the high number of primitive, heat generating IC's contained inside, along with multiple boards stacked together.  The RF package for the Satellite 80 is identical in appearance to the Satellite version, other than the front label says LCP 2080L.  Heads were available in either black or off-white.

The Satellite 80 was a VHF-only phone made in three models as follows:

LCP 2080   -   50 Watt Crystal controlled, 11 Channel  

LCP 2080A -  30 Watt Crystal Control, 11 Channel                                                                                         

LCP 2080L -  30/50 Watt Synthesized, 11/13 Channel

By 1980 Livermore had spun off the data division and the car telephone business was re-named just Livermore Communications.

Livermore's final product was the LCP 4080 (VHF) and LCP 8080 (UHF) "Satellite 80 II," a newly designed smaller mobile package with essentially the same control head as the Satellite 80. The Satellite 80 II was in my opinion a complete disaster, both the head and the radio package were troubleshooting nightmares. The transmitter RF power amplifier was unstable and would go into oscillation, feeding off-frequency RF back through the duplexer and blowing out the front end of the receiver. The Satellite 80 II was made for a very short time; Livermore Communications went out of business in approximately 1983.

Livermore Data "Satellite" RF Package, Same appearance for all prior to "Satellite 80 II"

Livermore Data "Satellite 80"

CLICK HERE FOR SATELLITE 80 HEAD PHOTO FROM MANUAL 

Livermore Communications "Satellite 80 II" (1982)

Shown below is the RF package for the Satellite 80 II.  There was a newer looking control head for the Satellite 80 II, similar to that above, but with colored graphics on the lenses.  Actual production models of that head may have never existed, as the Satellite 80 II RF package below was supplied with the regular Satellite 80 head as shown above (but modified for use with the 80 II.)

HARRIS RF:

Harris RF of Rochester, NY entered the IMTS car telephone market with their model RF-150, in approximately 1973, which appears almost identical in physical appearance to a 1966 vintage GE MASTR Executive I mobile radio. The RF-4900 Series "universal" IMTS control head used with this set had self contained supervisory logic and required various jumpers to be set to program the mobile number. The head appeared similar to the Motorola MJ equipment, and was also sold separately for use on other makers' equipment.  It was also available with Secode 2805 Hz interrupted pulse signaling for the RCC market.  See the photo of the 4900 Series control head below under "Aftermarket IMTS Control Heads."

This equipment was superseded by the completely different CT-1555 radio drawer in the late 1970's, and by the "Alpha 2000" series in 1980.  The "Alpha 40" used the control head shown below, with the CT-1555 radios, but still required an outboard  logic package in the black plastic add-on housing.  The initial offering of the CT-1555 radios seems to have occurred with the RF-4900 Series rotary dial control head as shown later in "Aftermarket IMTS Control Heads."  The Alpha 2000 used the same basic control head as the Alpha 40, however all supervisory logic was finally internal to the radio package itself.  All of the Harris Alpha radio packages are of superb quality, particularly the Alpha 2000 sets (see below.)

Harris also sold the "Alpha 40" as a universal accessory unit which could be applied to the radio packages of almost any other manufacturer's equipment.  This was mounted in an ABS plastic housing designed to be affixed to the top of the existing radio housing with double-sided tape.  The control head was the Alpha 40 "cellular" style as shown in the advertisement above.  Harris today has become a major military communications contractor and a manufacturer of broadcast transmitters and other gear, as well as the current owner of the old GE two-way radio empire.

INTEGRATED SYSTEMS TECHNOLOGY:

Integrated Systems Technology of Garland, Texas, as described in the attaché phone description above, also made the Tel-Com 150B, an IMTS / MTS mobile telephone, priced at $ 2475 in 1975, and the 150-5375 IMTS control head used with it was available separately for $ 592.

CLICK HERE FOR AN EXAMPLE OF A 1975 AD FROM INTEGRATED SYSTEMS TECHNOLOGY

JOHNSON MT-500 SERIES:

The E.F. Johnson Company of Waseca, Minn. offered a solid state IMTS mobile telephone in approximately 1981, usually referred to as the MT-584 (UHF)  and MT-574 (VHF) series. It was a conventional synthesized mobile radio except for an added duplexer, and supervisory signaling was carried out in the control head.  The Johnson IMTS head was a modified U.S. Communications "Callmaster" circuit design in a housing similar to Glenayre heads (see photo below.)  These mobile drawers were usually sold without heads.  Johnson had purchased the rights to the U.S. Communications "Callmaster" series self contained IMTS control heads in the early 1980's from U.S. Communications of Idaho. The Johnson sets were not common.  Johnson also manufactured a 1972 vintage UHF mobile telephone radio package, apparently intended for use with a customer-supplied control head and supervisory package, primarily for RCC use, which may have been used by some Bell customers who privately owned their equipment. The E.F. Johnson company of Minnesota went out of business in approximately 2006, although the company name remains as a firm in Texas which apparently re-sells equipment actually manufactured overseas.

The example below is a UHF MT-584 Series which was found mated to a Glenayre GL-2021 control head.

AEROTRON:

Aerotron was an old-line mobile radio manufacturer which made one mobile telephone package in the mid 1970's through the early 1980's.  Typical model numbers would have been 600TT30 or 600TT60 for the VHF drawers and 800TT30 for the UHF version. .  This equipment was unremarkable in design and used crystals for frequency control, with a self contained duplexer of rather flimsy and crude construction.  The Aerotron radio relied on an external supervisory signaling package such as a Harris Alpha 40 (see photo below,) a Secode VP series head, or a self contained control head such as the Harris RF-4911 or Glenayre GL-2000. Most examples found by the author were attached to Harris Alpha 40 packages. The original intent of the design was to be used with a Secode VP-1 RCC control head with built-in decoder.  The 600TT30 is a 30 Watt unit while the 600TT60 is a 60 Watt design.  In approximately 1980 a synthesized version of this radio was developed, and marketed as the "Synthesized Amtel."  Presumably the crystal controlled version was simply called "Amtel."  The Aerotron advertising showed the Synthesized Amtel used with a Glenayre 2020 series control head.

Aerotron was located in Raleigh, North Carolina until the late 1990's, when they merged with Repco of Florida and moved the plant to Repco's address in Florida.  Both Repco and Aerotron went out of business in approximately 2004, and the contents and remains of the plant were dumpstered.  The Aerotron name is now owned by a radio tower maintenance firm.  It is believed that Aerotron and Repco were victims of the cell phone revolution and such products as the Nextel "push to talk" handsets.

INTERNATIONAL SYSTCOMS:

International Systcoms was a Canadian company which manufactured a number of MTS mobile telephones beginning in the late 1960's or early 1970's, usually prefixed by the model number VTR-, made primarily for the Canadian market. Typical models were the VTR-7 and the VTR-74, both manual MTS telephones. The radio packages of these telephones found their way south of the border where they were often mated to Secode, Glenayre, Callmaster and other aftermarket IMTS control heads. The Systcoms equipment was ruggedly built, if a bit crude in appearance.  The U.S.A. sales office was Systcoms, Inc. and was located in Plattsburgh, New York.

Shown below is a 1974 dated VTR-74 series MTS car telephone intended for the Canadian market (note the 13 channels versus 11 in the U.S.A.) but sold in the American market.  The control head detaches from the radio package and can be mounted independently.  This phone had the interesting feature of scanning for the 600/1500 Hz signaling tones.  The model shown below was used by Empire Communications (Santa Rosa) as a Rural Radiotelephone Service unit in northern California with the "Compact" version control head mounted on the front.  There was also a "Contempra" control head built into a Northern Electric "Contempra" telephone.  Systcoms also manufactured the VTR-474, a UHF version of the same telephone. 

Systcoms' last product was the VTR-2084 "Micro Classic" IMTS phone.  Systcoms appears to have been purchased by Novatel, which brought out its one and only IMTS mobile phone as an updated Micro Classic, which they called the "Aurora," and which used a Novatel cellular style head (see Novatel, below.)  The head contains two pushbuttons on the lower edge; one is the "on-off" button and the other is the "horn" button often connected to blow the vehicle horn when a call was received.

CLICK HERE FOR MORE PHOTOS OF SYSTCOMS AND NOVATEL EQUIPMENT

XILEX:  

Xilex was a rather short-lived manufacturer which made at least one model of IMTS telephone before going out of business in the early or mid-1980's.  Apparently some of the Xilex engineers designed the later Transcon IMTS phones (see data below.)  I need more information on Xilex!  

AFTERMARKET IMTS CONTROL HEADS

A number of "modern" appearance control heads were sold in the late 1970's through the early 1990's to be retrofitted onto earlier mobile telephone systems. These newer heads offered self contained IMTS signaling and supervisory operation, were keyboard programmable, and offered memory number and roaming channel lists. The principal makers were Glenayre, Johnson and US Communications (later absorbed by E.F. Johnson). Secode and Harris RF also offered add-on control heads which could be made compatible with other maker's equipment.  The manuals usually contained application sheets explaining how to configure them to function on assorted makers' RF packages.

SECODE:  Beginning in the early 1960's, Secode manufactured a variety of mobile telephone control heads, primarily for the RCC market but some of which were also used with MTS telephones.  The GE-Secode head for the Executive II shown above (Secode VP-5) was one of their last products for this market.  It is unknown whether it ever made it to production, but Secode also attempted to market an interesting "cordless handset" accessory for an IMTS phone, which allowed the handset to be removed from the vehicle and taken some distance away.  At least one aftermarket cell phone company (located in California)  copied the same concept, using a conventional cordless telephone handset with a Johnson AMPS cellular phone radio drawer.  These ideas never bore fruit, presumably because IMTS was already near its end by the time the concept was created, and hand-held self contained cellular telephones were already becoming available, in an even smaller size.  Secode was the most prolific manufacturer of tone signaling devices and control heads and manufactured the VP-1 through VP-5 series control heads, the VP-5 being the only IMTS unit in the series.

GLENAYRE: Glenayre, a Canadian based company, began producing aftermarket digital control heads for existing equipment in approximately 1977. Their first products were the GL-2000, and later the GL-2020, followed by the GL-2021.  The 2021 has extra features but otherwise appears identical to the 2020.   In the 1980's, Glenayre would offer a combination cellular/IMTS telephone which consisted of their GL-3000 control head, mated to Spilsbury VHF equipment and Glenayre manufactured cellular equipment.. The Glenayre aftermarket heads were extremely popular in the 1980's, usually replacing rotary dial heads on older Motorola and GE "MJ" IMTS equipment and for converting older duplex MTS-only equipment to full featured IMTS.  Glenayre heads were available in black and an off-white. Glenayre ceased marketing IMTS equipment in the 1990's although they still marketed Autotel equipment in Canada (Autotel is a proprietary format similar to IMTS and used only in Canada.)

The GL-2000 is shown below.  Undoubtedly one of the ugliest IMTS control heads, it has a grille where one would expect a dial, with nothing behind it, and the small momentary pushbuttons for the channels also act as the number pad when dialing.  There are round LED indicators above each channel button, which indicate the channel the radio is operating on (as well as showing scan activity) and there is a small numeric LED display below the Glenayre logo which indicates the number being dialed.  The GL-2000 could be supplied with a cable to match almost any radio package on the market.  The head is programmed by holding down several specific buttons while powering it up, and entering the channel list and phone number.  The memory board uses three small aspirin-shaped nicad back-up batteries which leak acid vapors onto the adjacent circuitry and cause moderate to extensive corrosion.  There are various versions of firmware in the GL-2000, which mainly controls how the scan display will be handled.  There are also various versions of the interface board configurations in the GL-2000, which determine which radio telephone drawer the head will be used with.

Shown below is a white GL2000 installed in a Z-28 Camaro in 1984, courtesy Lance from Las Vegas:

Below is a Russian VHF mobile telephone from 1980.  Notice the similarity to the Glenayre GL-2000 above, designed at the same time.  Who copied whom?

CLICK HERE TO SEE MORE RUSSIAN MOBILE PHONES

Below is an example of the GL-2020 / 2021 head.  These heads were extremely popular and similar to cellular heads.  As with the 2000 series, they were made available with many interface cables to function with practically anyone's radio package.  Programming is accomplished by depressing a certain series of keys in a certain order and then following a programming matrix described in the service manual. The 2020 and 2021 series contain a speaker for on-hook dialing but do not feature a speaker-phone option. All the Glenayre heads had the ability to store two separate telephone numbers (ANI's) and could give billing interval beeps to the user so that he could determine what the call was costing (remember...these were the days of $ 1.00 per minute IMTS phone calls!) It was also possible to create home and roam channel lists, and specify which ANI number was to be used on which channel, which channels were MTS and which were IMTS, and so forth.  The 2021 head was somewhat more expensive than the 2020 and for some reason one often finds 2020 circuitry hidden inside 2021 series plastic shells.  One can only wonder whether this was some sort of dealer chicanery? 

HARRIS RF:  As mentioned above, the Harris Corporation sold a self contained IMTS control head with rotary dial, the RF-4900 series, which could be used with their own RF-150 mobile radio package or with other equipment such as the Motorola TLD-1000 or TLD-1100. Available in beige, white or black. This was superseded in the 1980's by the Alpha 40 control package, which also could be added to most any older radio made by other manufacturers (see above description and photos.)  RF-4911 "revertive call" model is shown below (VHF labeled.)  This head was disliked by dealers as it had a number of issues with reliability as well as a confusing method of operation.

U.S. COMMUNICATIONS: (Callmaster)  The Callmaster MT-270 (RCC) and MT-200 / MT-300 (IMTS) were fully IMTS self contained aftermarket control heads made by U.S. Communications in Idaho, inside what was essentially a GTE / Automatic Electric Touch-Tone® "Starlite" princess-style housing.  In the early 1980's,  U.S. Communications was absorbed by E.F. Johnson, and the Idaho facility was closed.  The Callmaster generated a rather high amount of heat from its internal logic and required a rather thick base plate to act as a heat sink.  It also required a special very lengthy keypad sequence to program it, which can best be described as apocryphal.  The Callmaster heads were available in beige or black.  The MT-200  heads were used by Pacific Telephone in 1982, connected to either a GE Executive II RF duplex package or a Motorola Pulsar 100 radio.  They were also sold by Western Mobile Telephone in Anaheim, California throughout the 1980's to early 1990's either by themselves or attached to such radios as refurbished 1960's GE MASTR CC56 RF packages or MASTR Executive II units..  U.S. Communications has no relation to United States Communications of Los Angeles, an early importer of PYE British RF packages which were made into MTS telephones with the addition of a solid state decoder and a modified Automatic Electric "Starlite" telephone (see ARC/PYE "Cambridge" above.)  Note that the AE "Starlite" plastic housings were subject to severe "yellowing" and even "browning" caused by a photochemical reaction in the flame-retardant additive applied in the plastic molding process.  The example below is a case in point.  An additional major aggravation concerning these heads is that the manufacturer thoughtlessly created special firmware masks in ROM regarding the programming, on a per-customer basis, such that there is no single, universal password which initiates the programming.  For example, the Pacific Telephone MT200W heads use a different password phrase than regular MT200's, and the MT270 RCC model uses yet another password.  If you need the passwords and programming strings, contact me and I will share what I have.

E.F. Johnson:  Johnson manufactured an aftermarket control head which resembled the Glenayre 2020 series, and which was probably intended to be sold with the Johnson MT-580 Series RF packages of the 1980's although it was sold separately.  It is believed that the Johnson head was the final design from the old U.S. Communications company of Idaho which was absorbed by E. F. Johnson in the early 1980's.  There was apparently a final U.S. Communications head design which was similar to or identical to this one.  This Johnson IMTS head looks similar to the one and only "Western Union" cellular AMPS head of the same era.  The Johnson head has a built-in speaker for on-hook dialing but does not feature hands-free operation.

THE FINAL YEARS

1983-93

None of the major manufacturers offered new mobile telephone models after 1982. They were gearing up to provide cellular equipment instead. What IMTS equipment they offered after 1982 was their existing 1970's design equipment, in some cases with more modern looking control heads, or modified and upgraded to operate with a cellular package, so that both modes were available from a single handset. During the late 1980's and early 1990's, a few small firms produced specialized IMTS radios in small quantities, which filled in the gap left by the departure of Motorola and GE. In some cases, specifically the hand-held portables, these IMTS radios were not true IMTS mobiles at all, but just conventional mobile radios which had been modified to provide duplex operation and IMTS signaling, or were half duplex (see Yaesu example below.)

YAESU TRAVELER HANDHELD IMTS:

An interesting "portable" IMTS telephone was introduced by the Japanese company Yaesu in 1982. It was called the "Traveler IMTS" and was available in either VHF or UHF versions. Built on the platform of the commercial FTC-2205 handheld radio, the Traveler was capable of operation on either RCC or Bell System frequencies, in either the MTS or IMTS formats, or the proprietary "SMART" format developed by Secode (not used by the Bell System.) The unit was not full duplex, and not really IMTS capable at all.  What the unit actually did, was it sent IMTS signaling without requiring certain acknowledge tones from the central office before proceeding further, as a conventional mobile would.  In other words, the Traveler "fooled" the telephone company base station into believing it was talking with a conventional IMTS mobile unit, and assumed that the station was sending the various acknowledge tones.  The Traveler would drop carrier as soon as signaling was complete, and from then on operate in a push-to-talk mode. It was necessary to learn various keypad routines to use the unit.

The Traveler had a built-in timer which would pulse the carrier from time to time to prevent the telephone company base station from thinking the mobile subscriber had gone out of range or had terminated the call without transmitting the disconnect signal.  The base stations were normally set to disconnect a call automatically if carrier from a mobile was not detected for a pre-determined amount of time.

The Yaesu Traveler appears to have been sold from 1982-1984; I am not certain of the ending date for sales.  It was the only example of a hand-held "IMTS" telephone to be widely marketed and advertised and the cost approached $ 1000.  Operation of the Traveler is best described as "inscrutable" and a fair amount of time studying the manual was necessary before attempting its use.   For some reason there was a quantity of both VHF and UHF versions of the Yaesu left as new-in-box items, on the market in the late 1990's, but many of them were missing EEPROM chips.  It is unknown whether the units were ever completed in the first place, or if the chips were removed as part of some sort of salvage sale.  Small quantities of these radios continue to show up on eBay in unused condition on an occasional basis.

UNIDEN HANDHELD IMTS:

Uniden manufactured a hand-held IMTS radio similar to the Yaesu unit above, in approximately the same time frame, although I have no other information on it.  It appears that Yaesu was the only manufacturer which committed itself to a rather extensive advertising campaign, as mentioned above.  Uniden appears to have preferred to market logic packages and telephone subassemblies to other manufacturers, to be badged with their own logo.

NOVATEL AURORA:

International Systcoms appears to have been merged into or bought by Novatel, and their last product, the "µ-Classic," became the Novatel "Aurora."  The Aurora was essentially an upgraded Systcoms "µ-Classic" unit as shown above, but came with a different, "cellular-looking"  control head, and the connectors on the RF package were changed to  more conventional ones which were the same as used on some early AMPS cellular RF packages.  The internal circuitry was probably also somewhat upgraded from the Systcoms equipment, and this telephone dates from approximately 1984.  The Aurora was unique in having multiple electronic ring tones available, including a musical one.  The final version of the Aurora, in the mid 1980's, offered a "piggyback" cellular unit consisting of the AMPS model Aurora cellular RF package on top of the Aurora IMTS RF package.  It is unknown if a UHF Aurora was ever manufactured.

CLICK HERE FOR MORE PHOTOS OF AURORA

TRANSCON TC-105 and TC-102 MOBILE TELEPHONES:  

Transcon was a Canadian based firm which briefly marketed a VHF mobile telephone manufactured in Taiwan, which appeared to be a conventional dash-mounted radio modified to be full duplex, with IMTS signaling, and certainly ugly.  The Transcon signaling logic and control design is an outgrowth of that originally created for the Xilex mobile phones, the Transcon equipment being apparently designed by one of the former Xilex employees.  The Transcon phones were a rather peculiar arrangement where the transceiver package was apparently intended to be under-dash mounted although it would technically be possible to trunk mount them with an extension cable to the handset.  The Transcons were described as requiring a "technician handset" to be programmed, although it turns out that there is a "program" switch on the internal circuit board which if set, allows the existing handset to program the unit.  The connection to the handset was made with a "modular" style telephone cable.

The TC105 and TC102 differ in terms of the feature set, memories and similar options, but are almost identical.  It is believed that the Transcon phones were only made in VHF versions.  The circuitry is at least partially, or perhaps entirely manufactured by Uniden.

Interestingly, the Transcon radio internally generates dial tone as soon as the handset is taken off the cradle, rather than opening the handset audio line to allow dial tone audio supplied from the telephone company terminal once the mobile ANI has been processed and approved. This has the disadvantage that it is impossible to gauge the signal quality coming from the land terminal, and can also give a false sense of security as to where dial tone might be available.  A number of Transcon units were purchased by regional Bell operating companies in the final years of IMTS, for use by service and employee vehicles, after Motorola and GE were no longer supplying equipment.  For example, the Transcon units were used by Pacific Bell employees and IMTS field service vehicles through 1995.

PACE EQUIPMENT:  

Pace, a CB equipment manufacturer, attempted in the late 1980's to market a synthesized IMTS radio telephone. It was similar to the Transcon radio and is doubtful that many were sold. The control head appears to have been a Johnson self contained IMTS unit. Few were sold. [Photo needed!]

GLENAYRE:  

Glenayre, the Canadian based company described above, made a final model IMTS and cellular combination telephone in approximately 1986, consisting of two radio packages (one IMTS and one cellular) piggy-backed together and feeding a Glenayre GL-3000 control head.  [Photos to follow]

HARRIS ALPHA 2000 :

 Harris, mentioned above, offered their final IMTS mobile telephone as the Alpha 2000 series. The Alpha 2000 was a very advanced and superbly made high power mobile unit with a built-in supervisory package which used a similar control head to that used on the earlier "Alpha 40" equipment. That control head, which appears identical to a standard cellular phone head of the mid-1980's, used a serial communication line to control the supervisory package in the radio. The original Alpha 2000 was programmed with a programmer which used "one time" 32x8 "proms" as used in first generation cellular phones.  The Alpha 2000 "E" model, the final one, utilized a re-programmable EEPROM chip, but required a separate programmer, consisting of an Epson HX-20 computer and printer plus some interface hardware, in order to enter the mobile ANI and other parameters into the radio's memory chip. The Alpha 2000 was made for VHF and UHF systems, and a UHF TV-channel sharing model was also made for a number of "Metro" 470 MHz mobile telephone systems apparently unrelated to the Bell System.  The final Alpha 2000-ET had an extra socket on the front with provisions for stacking a cellular transceiver on top, for those customers who needed both capabilities. 

[Photos to follow]

MOTOROLA PULSAR III: 

 The Motorola Pulsar III was not really a new product, but rather a modified Pulsar II RF package with a Dyna-Tac 6000X cellular handset instead of the standard Pulsar II.  The Pulsar III was also available after 1983 as a combination IMTS and Cellular package, with switching between the two.  The cellular section was provided by a Motorola Dyna-Tac first-generation AMPS cellular RF package.  Both the Dyna-Tac and the Pulsar III were modified from stock to accommodate the dual operation.  There as a standard Pulsar III unit for IMTS only operation, and a slightly different one which allowed interface with the cellular RF package.  The model numbers were either T- prefixed as the Pulsar series usually were, or F33EDA--- as the alternate number.  A field conversion kit was available to convert the "standard" Pulsar III to the cellular capable version.  It is believed that few were made in either configuration.  Motorola briefly advertised both versions at a deeply discounted price for direct sale, in the back pages of Communications Magazine and probably other venues, which was unusual.

[Radio drawer photo to follow]

SPILSBURY: 

Spilsbury was a pioneer Canadian manufacturer of HF portable radios for logging and wilderness forestry applications, beginning as Spilsbury and Tindall.  It ventured into the mobile telephone market in the late 1980's making at least one small, modern duplex RF package, evidently without a control head.  They were used usually with the Glenayre GL-2020 and GL-2021 control heads in the United States, and possibly with GL-3000 series heads at the end of production.  These radio packages were made in both VHF and UHF versions.  They were also made for Canadian Autotel or BC-Tel systems which apparently were similar to IMTS and operated on the same channels, but those used the GL-2031 and GL-2035 heads from Glenayre.  Spilsbury was bought out by another concern in the early 1990's and is no longer in business.

THE PACIFIC BELL CALIFORNIA IMTS SYSTEM

Pacific Telephone and Telegraph, which became Pacific Bell after the divestiture, ran the largest mobile telephone system in the world, with over 12,000 subscribers at its peak. Until 1982, the system was not remarkable and far from progressive, remaining MTS with all calls being processed manually. At the end of 1982, the system had finally converted to IMTS with seven digit mobile numbers. Pacific Bell was likely the last major mobile telephone system to convert to IMTS. Pacific Bell began IMTS with the conversion to a Motorola EMX mobile telephone computer system, which involved two massive mainframe computers and switches which controlled the entire statewide mobile telephone service. It called its service "IMTS-B." One EMX was located in Anaheim, California, and the other was in Sacramento, California. All signaling and mobile telephone traffic, by necessity, now had to be carrier-trunked to either Sacramento or Anaheim for processing. Any major problems with the centrally controlled EMX system resulted in service failure for an entire half of the state. The EMX, a multi-million Dollar system, was in many respects a failure, more so as it aged. The only other EMX ever employed was in a mobile telephone system in Saudi Arabia, and the current status of that system in unknown. It has been commented that the flaw in the EMX system was the software, in that third party software for the same functions as that supplied with the EMX by Motorola, functioned flawlessly.

The EMX offered many advanced features such as "follow me roaming", "call waiting,", and 911 emergency call routing (but to a central 911 center staffed by Highway Patrol dispatchers). Most of these features never worked properly or were never implemented. Voice transmission quality through the system was poor, particularly the mobile to land circuit. Mobile callers sounded like they were calling from another solar system, and a typical failure mode would be for the EMX to still process call routing, but fail to complete the audio circuit, or have audio available but fail to complete the call routing.

Pacific Bell appears to have spent its entire mobile telephone budget on the EMX switches, allowing the balance of the system to fall into disrepair and dilapidation. The radio equipment at the land stations still used the early 1960's vintage Motorola receivers left over from the old MTS system, and hybrid Motorola high power transmitters from the same era remained as well. Field service technicians reported such conditions as outside mounted receiver cabinets being full of rainwater due to deteriorated gaskets on the cabinet doors, transmitters running at a fraction of their power output capabilities due to worn out tubes and power supply malfunctions. At any given time, one or more of the voting receivers used in wide coverage systems would be malfunctioning, or supplying audio to the system at a vastly different level than the others. As a result, subscribers began to migrate to cellular service as soon as it was available, and Pacific Bell then began to complain that the IMTS system was "not profitable." This author pointed out to them that no system could be profitable if no subscriber could process a call due to equipment malfunctions, but this seems to have fallen on deaf ears.

Pacific Bell "officially" terminated all IMTS service in May, 1995, after extending the termination date several times. On the last "official" day of IMTS service, the system in Northern California was operating so poorly that it is doubtful anyone could complete a call anyway. A check of the Southern California system several weeks before "the last day" revealed a complete inability to get dial tone on any IMTS channel run by Pacific Telephone from San Diego to San Luis Obispo. A check of the IMTS VHF channels in Northern California the week after the "last day" turned up the surprising fact that the system was still on the air, and a number of mobiles were using the system ! A call to Pacific Bell resulted in the response that employees and company mobiles were still using the system, but that all public customers had been disconnected. This was in fact not true, in that a check of all active mobile numbers in my county showed several private customers still answering and being able to process calls. The reason for this remains a mystery; possibly there was some confusion in deleting active mobile numbers from the database.

At the end of May, 1995, the Pacific Bell IMTS system was taken off the air in its entirety. For a few weeks afterwards, automatic CW identifiers brought up all of the transmitters and identified them with a string of callsigns, every ten minutes, then dropped the carriers. After about a month, that activity ceased also. Today, the channels are vacant and largely quiet. In the late 1990's, many channels were re-licensed to paging companies, but as pagers became passé and  the paging systems were taken down, the channels were once again reassigned, in this case to conventional land mobile users.

Of note is that the California GTE and Con-Tel IMTS systems survived longer, as well as having started with IMTS before Pacific Telephone did. The Los Gatos, California GTE system was still on the air in 1997 although it is believed that virtually all IMTS systems on Bell channels are off the air today in the United States. There is still at least one IMTS system still on the air, the Schuylkill Mobile Fone, Inc. VHF IMTS system in Pottsville, Pennsylvania.

An interesting note is that in approximately 2003, the FCC auctioned the long-abandoned low band 43 MHZ "Z" series MTS channels originally occupied by Pacific Telephone and other Bell operating companies on the western coast. These channels were purchased for a small sum, relatively speaking, by private interests and a use for them has yet to be determined.

Thanks to Empire Communications of Santa Rosa, California, without whom this page would not have displayed anywhere near the number of phones it does.

POSTSCRIPT:  

If you are interested in mobile telephone history, I would like to hear from you. Also, if you have a Bell or independent Telco IMTS or MTS car telephone system still operating in your vicinity, I would especially like to know about it. I am looking for many MTS mobile phone items to add to my "museum" and for photos on this web page. I specifically would like to find service manuals for any Canyon Communications products, service manuals for any late Systcoms products, service manuals for Novatel Aurora IMTS VHF car phones, Western Electric 41A series control head parts, smaller IMTS radiotelephone terminal equipment, advertising literature, Bell System Practices publications on MTS and IMTS radio telephones, service manuals for  and examples of Motorola Motrac - Motran and Micor "Z" channel lowband equipment, any ITT mobile telephones, any Symetrics mobile telephones, and much more. If you have any photos of early car telephones, please share them, credit will be given.  Help save this history from going to the dump! I would also like to hear from any foreign visitors to this page, who might have information about vintage radio telephone systems in their country.

This page maintained by Geoff Fors, WB6NVH.   E-mail me at the address shown on my home page.

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Ver. 3/05/2010