Transmitting and reproducing system having improved noise reduction

Abstract

A transmitting and reproducing system includes an encoder for selectively combining at least four signals for transmission along two channels. At least three of the signals are combined in a predetermined amplitude and phase relationship to form a first unmodulated signal and at least one of the three signals is used to vestigially modulate a carrier. The unmodulated signal and the modulated carrier are combined for transmission along one of the channels. A different grouping of three of the signals are combined in a different predetermined amplitude and phase relationship to form a second unmodulated signal, and at least one signal different from the first modulating signal is used as a second modulating signal for vestigial modulation of the carrier. The second unmodulated signal and the carrier modulated by the different signal are combined for transmission on the second channel. The signals used to modulate the carrier are passed through noise reduction circuits that have frequency response characteristics that compress signal components above a frequency that depends upon the amplitude of the signals passing through the noise reduction circuits. The reproducing part of the system includes a decoder that selectively combines the composite signal on each of the channels with the demodulated signals from the two signals that were originally modulated, thereby reproducing two main signals without interference.