<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> <P> In 1949, AT&T commercialized Mobile Telephone Service . From its start in St. Louis, Missouri, in 1946, AT&T 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 80 lb . </P> <P> 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 . </P>

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