GB632778A - Improvements in telephonic transmission systems using multiple channel carrier currents - Google Patents

Abstract

632,778. Multiplex systems. SUEUR, R. C. May 11, 1945, No. 11846. Convention date, Nov. 25, 1943. [Class 40 (iv)] The voice frequencies of one channel A1 and side-band frequencies obtained by modulating a carrier wave f1 with voice frequencies B1 of a second channel are transmitted together as a group. The filter F1 accepts the original frequencies (0-4 kc/s.) and F2 accepts the upper side-band (4-8 kc/s.) produced when f1 is modulated by B1 in the modulator M1. A carrier f2 is modulated by the group frequencies in a modulator M2 and the lower side-band accepted by a filter F3 is applied with five similar groups A2, B2 ... A6, B6, making twelve channels in all, to a group modulator M3, where a carrier f3 is modulated. Before amplification at A and transmission to line L, the lower band is finally selected by a filter F4. The operations are reversed at the receiver. The twelve channels occupy a band of frequencies of 48 kc/s. between 60 and 108 kc/s. In a modification, the groups are fed through an additional stage of modulation before they are assembled together in one band.