Before the late 1980s and the arrival of PCS mobile phone service, GTE offered Improved Mobile Telephone Service ( IMTS ) on VHF ( 152 MHz ) and UHF ( 454 MHz ) frequencies in Los Gatos.
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Mobile radio telephone systems such as Mobile Telephone Service and Improved Mobile Telephone Service allowed a mobile unit to have a telephone number allowing access from the general telephone network, although some systems required mobile operators to set up calls to mobile stations.
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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 current state of the art, fourth generation ( 4G ) native-IP networks.
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