The FMX™ Stereo Broadcast System

A new broadcast service, developed jointly by CBS and the National Association of Broadcasters, has proven highly effective for improving the quality and range of FM stereophonic reception. Compatible with existing service, the new transmission format additionally incorporates a compressed stereo difference signal, in quadrature at 38 kHz. A unique adaptive expander in receivers provides 20 dB attenuation of noise and distortion components under conditions of adverse reception. The stereo service area typically is increased three-fold, to the geographical limits of equivalent monophonic reception.