1. A physical object or quantity, for example a moving clock hand or an electrical voltage, that is used to measure or represent some other quantity, and is hence analogous to it.
2 A family of electronic devices that represent other physical quantities by continuously varying voltages rather than the two discrete voltage levels used in DIGITAL devices.
For example the output voltage of an analogue microphone follows exactly the changes in sound pressure of a speaker's voice. All telephone, radio and television systems prior to the 1990S were based on analogue electronics.
The disadvantage of analogue devices compared to digital ones is that any physical effect that changes the voltage - such as non-linearity in the conductors, stray electrical or magnetic fields, power supply fluctuations – will corrupt the data. The advantage of analogue devices is that they may operate faster than digital devices, or store data more densely, since they avoid the overheads incurred in digitizing the data.