Abstract: Multi-channel telephone communication is enhanced by the use of the adaptable threshold extension demodulator described in this patent. These devices permit adjustment of the threshold depending on the present loading of the baseband. By changing the characteristics of the feedback loop in the demodulator, the threshold can be adjusted for optimal performance. The sensor may take one of two forms. In a first embodiment, the sensor detects baseband loading by converting the baseband to a DC level. In another form, frequency selective filters determine the highest level of the baseband and convert that into an incremental level signal. In a variation of the second embodiment, a low-pass filter and a bandpass filter detect the loading directly from the IF signal.

Abstract: A system for distributing a television program with stereophonic audio via satellite includes a video base band, and audio left and right signals each frequency modulating spaced subcarriers. Special low level tone pulses are transmitted via the respective subcarriers when a television program with stereophonic audio begins and when it ends.Those receiving stations wishing to distribute stereo audio (as via cooperating local television and FM stations) merely detect and disseminate each subcarrier modulation. Receiving stations desirous of distributing monaural audio recognize the stereo program signalling pilot, and enable a left and right program summing amplifier to restore and furnish a compatable, full monaural audio signal.