The current analog cellular FM system in North America. It uses 30 kHz channels, and signaling is done superaudio.
The North American analog cellular phone system. The spectrum allocated to AMPS is shared by two cellular phone companies in each area or region (geographic market). This system was deployed during the 1980s and today it and its variants represent nearly 85% of the cellular voice systems installed throughout the world.
Analogue systems of mobile phones send information over radio waves as an electrical copy of the sounds picked up by the phone's microphone (in this case the human voice). The information is sent as a continuous flow of energy, so that only one conversation at a time is possible on any one frequency. More information on analogue and digital systems can be found at From dots to data: The story of digital transmission and data communication (Telstra ClassRoom, Australia) and What is the difference between analog and digital cell phones? (How Stuff Works, USA).