History of Mobile Telephone
and Cellular Telephone
The early days of mobile telephone systems.
In 1947 AT&T commercialized mobile telephone service.
From its start in St. Louis in 1946, AT&T then introduced Mobile
Telephone Service to one hundred towns and highway corridors by 1948.
Mobile Telephone Service was a rarity with only 5,000 customers placing
about 30 000 calls each week. Calls were set
up manually by an operator and the user had to depress a button on the
handset to talk and release the button to listen. The call subscriber
equipment weighed about 36 kg.
Subscriber growth and revenue generation were hampered by the
constraints of the technology. Because only three radio channels were
available, only three customers in any given city could make mobile
telephone calls at one time. Mobile Telephone Service was expensive, costing 15 USD per month, plus 0.30 to 0.40 USD per local call, equivalent to about 176 USD per month and 3.50 to 4.75 per call in 2012 USD
AT&T introduced the first major improvement to mobile telephony in 1965, giving the improved service the obvious name of Improved Mobile Telephone Service.
IMTS used additional radio channels, allowing more simultaneous calls
in a given geographic area, introduced customer dialing, eliminating
manual call set by an operator, and reduced the size and weight of the
Despite the capacity improvement offered by IMTS, demand outstripped
capacity. In agreement with state regulatory agencies, AT&T limited
the service to just 40,000 customers system wide. In New York City, for example, 2,000 customers shared just 12 radio channels and typically had to wait 30 minutes to place a call.
Radio Common Carrier or RCC was a service introduced in
the 1960s by independent telephone companies to compete against
AT&T's IMTS. RCC systems used paired UHF 454/459 MHz and VHF
152/158 MHz frequencies near those used by IMTS. RCC based services were
provided until the 1980s when cellular AMPS systems made RCC equipment
Some RCC systems were designed to allow customers of adjacent
carriers to use their facilities, but equipment used by RCCs did not
allow the equivalent of modern "roaming" because technical standards
were not uniform. For example, the phone of an Omaha, Nebraska–based RCC
service would not be likely to work in Phoenix, Arizona. Roaming was
not encouraged, in part, because there was no centralized industry
billing database for RCCs. Signaling formats were not standardized. For
example, some systems used two-tone sequential paging to alert a mobile of an incoming call. Other systems used DTMF. Some used Secode 2805,
which transmitted an interrupted 2805 Hz tone (similar to IMTS
signaling) to alert mobiles of an offered call. Some radio equipment
used with RCC systems was half-duplex, push-to-talk LOMO equipment such
as Motorola hand-helds or RCA 700-series conventional two-way radios.
Other vehicular equipment had telephone handsets, rotary or pushbutton
dials, and operated full duplex like a conventional wired telephone. A
few users had full-duplex briefcase telephones (radically advanced for
At the end of RCC's existence, industry associations were working on a
technical standard that would have allowed roaming, and some mobile
users had multiple decoders to enable operation with more than one of
the common signaling formats (600/1500, 2805, and Reach). Manual
operation was often a fallback for RCC roamers.
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