Abstract

An FM transmission system and method in which a gain control signal is generated and used to encode the audio signal in accordance with a predetermined compression curve. At the receiver the gain control signal is recovered and used to decode the audio signal, thereby providing a faithful reproduction of the original signal regardless of which compression curve is used. The compression curve can be tailored for optimum results for receivers with and without the decoding circuitry, depending upon the program material. The audio signal is delayed in the encoder while the gain control signal is generated, allowing the control signal to fully respond to changes in the audio signal without clipping the audio signal. The gain control signal is segregated from interfering with the remainder of the transmitted signal by restricting it to a low frequency bandwidth centered on the 38 KHz subcarrier for the L-R signal, and placing it in phase quadrature relation to the remainder of the transmitted signal. A number of different compression curve generators may be provided in the encoder to enable a selection among the different curves.