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Analog recording
Analog (or analogue) recording (Greek, ana is "according to" and logos "relationship") is a technique used for the recording of analog signals which, among many possibilities, analog audio and analog video for later playback.
Analog recording methods store signals as a continuous signal in or on the media. The signal may be stored as a physical texture on a phonograph record, or a fluctuation in the field strength of a magnetic recording. This is different from digital recording which digital signals are represented as discrete numbers.
http://en.wikipedia.org/wiki/Analog_recording