Abstract

Disclosed herein is a novel frequency division multiplex system for use in connection with transient signals such as speech and music signals. One embodiment includes a pair of comb filters, the response characteristics of which are staggered so that the pass bands of one comb filter are in alignment with the attenuation bands of the other comb filter. Each channel signal is filtered by its associated comb filter and then combined to develop a comb frequency division duplex (CFDD) signal for transmission over a transmission medium. At the receiving terminal the CFDD signal is decombined into the individual channels and passed through another pair of comb filters, the response characteristic of each comb filter being the same as that of the comb filter in a corresponding input channel. In another embodiment, a recording and playback system is provided to record the CFDD signal, i.e., two channels of information in a single track on disc or tape and to playback such recorded information. This invention is based on the observation that the attenuation of some of the frequencies in audio signals does not materially degrade the naturalness and intelligibility of the signals.