The word compander is composed of the words compressor and expander and describes a device with which signals are compressed on the transmitter side and expanded on the receiver side before transmission, namely due to the limited dynamic range of the transmission path. It is an electronic functional unit with which the amplitude and/or the frequency can be compressed and expanded.
The purpose of compression, which is also referred to as companding in the case of a compander, is to improve the signal-to- noise ratio (S/N) on the transmission link. The compressed signal experiences less noise interference on the transmission path for the same amount of noise interference, so the signal-to-noise ratio after expansion is better than without.
In sound transmissionin FM broadcasting, for example, a corresponding process, the Emphasis technique, is used. Companders are also used in acoustics for noise reduction and are integral components of radio and wired microphones.