Radio Telephone
What was used before cellular: IMTS and MTS
By Michael Losse:
"The hardware associated with this technology was massive by today's standard. The mobile units could weight 20 or 30 pounds and consume 30 or so amperes while in use. If the stereo was on, the 'spike' on the vehicle's DC power supply would almost destroy the speaker. I remember an old IMTS unit I had installed in a small sports car. It was easy to tell when the mobile telephone was about to ring because the vehicle's headlights would dim . . ."
"Improved Mobile Telephone Service, or IMTS, replaced [the earlier] Mobile Telephone Service and allowed a mobile subscriber to directly dial a telephone number. The design objective . . . was to maximize the operating range for a mobile telephone user. A single set of channels was intended to cover as much area as possible. To facilitate this, high powered transmitters operating on relatively low frequencies were used. These factors allowed system operators to cover the largest areas for the least amount of money."
"The system operators were companies licensed to provide mobile telephone carriers, much like the cellular carriers of today. In most major cities, serviced was provided by the local Bell Telephone Company, and a few private companies, sometimes called radio common carriers (or RCCs). Customers had the choice of selecting the carrier that provided the service they needed. However, the service was expensive, and the quality of the connection was poor."
From The Cellular Telephone Installation Handbook, by Michael Losse, Quantam Publishing, 1988.
Motorola TLD-1100 "MJ" IMTS Telephone, 1963. The text reads:
CONFORMS TO ALL IMPROVED MOBILE TELEPHONE SYSTEM REQUIREMENTS INCLUDING: Full 11-Channel Capacity for Unlimited Roaming; Automatic Channel Hunting; Home, Roaming or Manual Operation
PROVIDES BONUS PERFORMANCE FROM ALL SOLID STATE, BUILT IN MOBILE SUPERVISORY UNIT: Totally Silent Operation; Easy Installation of The One-Package Design; Minimum Maintenance from The Solid State Circuitry
Used in Bell territories. Equipment below used in some non-Bell territories.
GTE DTD/DTO Mobile Telephone. Illustration shows the dial control unit, manual control unit, a power/control cable, and the transceiver itself, along with the antenna.
By Geoff Fors:
"This unit is not IMTS but a 1962 manual, operator-assisted 'MTS' radio while the DTD was a 'Dial' radiotelephone. 'Dial' was a proprietary system built by Secode and GE which allowed direct dialing and automatic terminal operation, but it wasn't compatible with anybody else's system. It didn't offer marked idle or channel hunting as IMTS did. Independents (principally REA co-ops and Con-Tel) used 'Dial.' I am not aware of any Bell affiliate which ever used it. Con-Tel in southeastern California was still using Dial up into the early 1980's. Dial is not compatible at all with IMTS, but it is compatible (partially) with MTS. As far as I know, the last Dial phone manufactured was the GE MASTR series (1972), which came in MTS, MTS/IMTS, Dial or 'Identified Dial.' -- Geoff Fors
Product literature scans courtesy of Geoff Fors who maintains this remarkable page:
MOTOROLA EARLY LAND MOBILE EQUIPMENT INDEX, 1938-1946
http://www.mbay.net/~wb6nvh/Motadata.htm
Geoff is an ardent mobile radio enthusiast, please visit his site soon.
More IMTS madness? Of course. Take a look at a company newsletter describing the 1982 cutover in Pac Bell land:
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