Czechoslovakia as the first analog mobile radio telephone in the whole Eastern Bloc The B-Netz launched 1972 in West Germany as the country's second public commercial mobile phone network (albeit the first one that did not require human operators to connect calls) Radio Common Carrier 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 (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. 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 or handheld that a wired phone was trying to call them. Other systems used DTMF. Some used a system called Secode 2805 which transmitted an interrupted 2805 Hz tone (in a manner similar to IMTS signaling) to alert mobiles of an offered call. Some radio equipment used with RCC systems was half-duplex, push-to-talk equipment such as Motorola hand-helds or RCA 700-series conventional two-way radios. Other vehicular equipment had telephone handsets, rotary or push-button dialing, and operated full duplex like a conventional wired telephone. A few users had full-duplex briefcase telephones (which were radically advanced for their day). RCCs used paired UHF 454/459 MHz and VHF 152/158 MHz frequencies near those used by IMTS. See also Walkie-talkie List of mobile phone generations 1G 2G 3G 4G 5G Mobile rig Mobile Telephone Service - (A pre-cellular VHF radio system that linked to the PSTN)