The race to create truly portable telephone devices began after World War II, with developments taking place in many countries.
The advances in mobile telephony have been traced in successive "generations", starting with the early "0G" (zeroth generation) services, such as Bell System's Mobile Telephone Service and its successor, the Improved Mobile Telephone Service.
These "0G" systems were not cellular, supported few simultaneous calls, and were very expensive.
Several other countries then followed in the early to mid-1980s.
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