An alternate spelling for “analog,” often used in the U.K.
Literally, an analog is a replica or representation of something. Examples: In audio signals, changes in voltage are used to represent changes in sound pressure. On vinyl records, groove depth is an analog for sound pressure levels. On magnetic tape recorders, changes in magnetism are an analog for changes in sound pressure. Note that in all these examples, the signal analog is a continuous representation, as opposed to the quantized, or discrete “stepped” representation created by digital devices (see also “Quantization Error”). Since analogs rely on physical measurements, the accuracy of the representation will be limited only by the precision of available measuring techniques (not taking in account the characteristics of various storage media, transducers, etc.).