<P> In the United States, engineers from Bell Labs began work on a system to allow mobile users to place and receive telephone calls from automobiles, leading to the inauguration of mobile service on 17 June 1946 in St. Louis, Missouri . Shortly after, AT&T offered Mobile Telephone Service . A wide range of mostly incompatible mobile telephone services offered limited coverage area and only a few available channels in urban areas . The introduction of cellular technology, which allowed re-use of frequencies many times in small adjacent areas covered by relatively low powered transmitters, made widespread adoption of mobile telephones economically feasible . </P> <P> In the USSR, Leonid Kupriyanovich, an engineer from Moscow, in 1957 - 1961 developed and presented a number of experimental models of handheld mobile phones . The weight of one model, presented in 19kdn61, was only 70 g and could fit on a palm . However, in the USSR the decision at first to develop the system of the automobile "Altai" phone was made . </P> <P> In 1965, Bulgarian company "Radioelektronika" presented on the Inforga - 65 international exhibition in Moscow the mobile automatic phone combined with a base station . Solutions of this phone were based on a system developed by Leonid Kupriyanovich . One base station, connected to one telephone wire line, could serve up to 15 customers . </P> <P> The advances in mobile telephony can be traced in successive generations from the early "0G" services like MTS and its successor Improved Mobile Telephone Service, to first - generation (1G) analog cellular network, second - generation (2G) digital cellular networks, third - generation (3G) broadband data services to the state - of - the - art, fourth - generation (4G) native - IP networks . </P>

When were cell phones released to the public