The compandor — An aid against static in radio telephony

One of the important conditions which must be met by any speech transmission system is that it should transmit properly a sufficient range of speech intensities. In long-wave radio telephony, even after the speech waves are raised to the maximum intensity before transmission, there remain energy variations such that weak syllables and important parts of strong syllables may be submerged under heavy static. The compandor is an automatic device which compresses the range of useful signal energy variations at the transmitting end and expands the range to normal at the receiving end, thus improving the speech-to-noise ratio.