Analog
A method of transmitting information via energy waves. In the case of wireless phones, analog transmission is where the sound waves of a person's voice are converted directly to specific, continuously-variable characteristics of a radio wave, and vice-versa.
Analog cellular telephone networks were built in the 1980s. In the US, the AMPS analog technology was deployed, which is now considered a first-generation, or "1G" technology.
Analog wireless technology is being replaced by Digital wireless technology. Virtually all new phones are digital, although many can also use analog networks. Analog networks cover more area than digital, so analog-capable phones can often use analog service in locations where digital service is not yet available.
See: Analog Roaming