Phase shift data transmission systems having auxiliary channels

Claim 1

A data transmission system in which pulse coded data is transmitted from transmitting apparatus to receiving apparatus, I. the transmitting apparatus comprising A. a source of pulse coded data signals, B. at least one carrier signal source, C. means to phase shift modulate a carrier signal from said carrier signal source with data signals from said source of data signals, D. means to generate an auxiliary signal of much lower frequency than said carrier signal, E. means to frequency modulate said carrier signal with said auxiliary signal using a maximum frequency deviation much lower than the frequency of the carrier signal, such that the maximum phase shift of the carrier signal arising from said frequency modulation during any one pulse Interval of said data is much less than the minimum step phase shift utilized in transmitting said data, and II. said receiving apparatus comprising A. means to frequency multiply said carrier signal such that all the step phase shifts utilized in transmitting said data become substantially integral multiples of a complete cycle of the frequency multiplied carrier signal, B. means to frequency divide said frequency multiplied carrier signal to recover the frequency modulated carrier signal, and C. frequency discriminator means responsive to the output of said last mentioned means to detect said auxiliary signal.