System for phase division multiplex duplex communication over a

Details System for phase division multiplex duplex communication over a System for phase division multiplex duplex communication over a

1976-11-15

1978-02-21

Stewart, David L.

Telegraphy

Systems

Printing

178 58R, 179 25R, 179 15BP, 343175, H04J 1100, H04L 514

Patent

active

040754278

ABSTRACT:
A system for phase division multiplex duplex communication over a two-wire circuit has a master terminal and a slave terminal. The master terminal comprises a modulator and a demodulator jointly connected to a first end of the two-wire circuit and arranged to transmit an outgoing AM-signal with an essentially non-suppressed carrier component constituting a pilot signal and to receive an incoming AM-signal with a considerably suppressed carrier component having a frequency identical to the frequency of the pilot signal. An oscillator circuit is arranged to supply the modulator and the demodulator with a first and secnd, respectively, oscillator signal having a respective frequency identical to the frequency of the pilot signal and having such a relative phasing that at the demodulator the phase of the second oscillator signal is phase displaced 90.degree. relative to the phase of the pilot signal. The slave terminal comprises a demodulator and a modulator jointly connected to a second end of the two-wire circuit and arranged to receive the AM-signal with the pilot signal and to transmit the AM-signal with the suppressed carrier component. An oscillator circuit is arranged to supply the demodulator and the modulator with a third and fourth, respectively, oscillator signal having a respective frequency identical to the frequency of the pilot signal and having such a phasing relative so that at the demodulator the phase of the third oscillator signal coincides with the phase of the pilot signal while the phase of the suppressed carrier component is phase displaced 90.degree. relative to the latter.

REFERENCES:
patent: 3384824 (1968-05-01), Grenier
patent: 3518680 (1970-06-01), McAuliffe
patent: 3795772 (1974-05-01), Hill
patent: 3822366 (1974-07-01), O'Dea

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