The Advanced Mobile Phone Service is an American standard for analogue mobile telephony, developed by AT&T. It has been the predominant analogue standard used in the USA. The system has also been used in Canada, South America and some countries in the Pacific.
AMPS is specified in the mid 1980's as EIA-553. It operates in the 850 MHz band (824-849 MHz uplink and 869-894 MHz downlink) with a channel spacing of 30 kHz. AMPS makes use of FM for the modulation. A narrowband version (N-AMPS) that makes use of radio channels of only 10 kHz width is introduced in the early 1990's.
It uses the US Telecommunications Industry Association (TIA) IS-41 standard as the underlying network protocol.