1) A system that processes electrical signals by representing the original signal as a continuous function of the original signal. The sound pressure at the input of a microphone may be represented as a voltage level at the terminals of an amplifier, which then amplifies the voltage. Analog differs from digital in that the digital representation of a signal is
represented as discrete numbers.
2) The traditional method of modulating radio signals so that they can carry information. AM (amplitude modulation)
and FM (frequency modulation) are the two most common methods of analog modulation. Early U.S. cellular systems
carried phone conversations using analog; however, most now offer digital (or digital + analog) transmission.