The dbx Model 140 simultaneous encode/decode broadcast noise reduction system is a two-channel compressor/expander providing a minimum of 30 dB broadband audio noise reduction with a 10 dB increase in a system headroom. The two channels feature independent encode and decode circuitry. In the record mode, the system compresses the input signal by a 2:1 ratio, linear in decibels over a 100 decibel range. Upon playback, the circuitry produces an exact mirror image 1:2 expansion of the encoded signal. True RMS level sensing insures perfect encode/decode tracking for accurate transient response irrespective of phase shifts in the transmission or storage medium. There is no audible breathing, pumping or other coloration of the sound with this encode/decode system, and there are no pilot tones or routine calibration procedures necessary for its use. The dbx system eliminates tape hiss in recording and prevents the noise build-up normally encountered in transferring information from one recorded medium to another; it does not remove noise present in the original signal. The dbx 140 noise reduction system is built to professional standards using the latest advances in circuit design and technology and is fully warranted (parts and labor) for two years.