Mobile radio telephone

Mobile radio telephone (or 0G) systems preceded modern cellular mobile telephony technology. Since they were the predecessors of the first generation of cellular telephones, these systems are sometimes retroactively referred to as pre cellular (or sometimes zero generation) systems. Technologies used in pre cellular systems included the Push to Talk (PTT or manual), Mobile Telephone System (MTS), Improved Mobile Telephone Service (IMTS), and Advanced Mobile Telephone System (AMTS) systems. These early mobile telephone systems can be distinguished from earlier closed radiotelephone systems in that they were available as a commercial service that was part of the public switched telephone network, with their own telephone numbers, rather than part of a closed network such as a police radio or taxi dispatch system.

These mobile telephones were usually mounted in cars or trucks, though briefcase models were also made. Typically, the transceiver (transmitter-receiver) was mounted in the vehicle trunk and attached to the "head" (dial, display, and handset) mounted near the driver seat.

They were sold through WCCs (Wireline Common Carriers, a.k.a. telephone companies), RCCs (Radio Common Carriers), and two-way radio dealers.

Early examples for this technology:

Parallel to Improved Mobile Telephone Service (IMTS) in the US until the rollout of cellular AMPS systems, a competing mobile telephone technology was called Radio Common Carrier or RCC. The service was provided from the 1960s until the 1980s when cellular AMPS systems made RCC equipment obsolete. These systems operated in a regulated environment in competition with the Bell System's MTS and IMTS. RCCs handled telephone calls and were operated by private companies and individuals. Some systems were designed to allow customers of adjacent RCCs to use their facilities but the universe of RCCs did not comply with any single interoperable technical standard (a capability called roaming in modern systems). For example, the phone of an Omaha, Nebraska–based RCC service would not be likely to work in Phoenix, Arizona. At the end of RCC's existence, industry associations were working on a technical standard that would potentially 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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