GB608634A - Terminal installation for multiplex carrier-current telephony - Google Patents

Abstract

608,634. Carrier telephony. SOC. ANON. DE TELECOMMUNICATIONS. Dec. 4,1945, No. 32760. Convention date, Aug. 6, 1942. [Class 40 (iv)] [Also in Group XL (c)] In order to arrange the whole of the terminal system on a single standard rack, each group of 3 juxtaposed panels mounted on the rack carries the transmitting and receiving equipment for two channels, the two outer panels each carrying the low-frequency equipment of one channel and the central panel carrying the high-frequency equipment of both channels. The invention is described with reference to a system in which modulation (and demodulation) takes place in two stages first by a source of 8 Kc. and subsequently by one of the 12 frequencies 20, 24 ... 64 Kc. The channel transmitting equipment is situated on the front of the rack, Fig. 2, and the receiving equipment on the rear of the rack, Fig. 4. Panel 21, Fig. 2, contains the input voltage limiter 1, voice frequency band-pass filter 2, modulator 3 producing both side bands of 8 Kc. and band-pass filter 4 passing one (the lower) side band only, which is then fed to the high-frequency panel 22 where, in modulator 5, it produces side bands of 20 Kc., the lower one of which, selected by band-pass filter 6, is fed in common with the outputs from other channels to the outgoing group repeater on panel 18, and thence to line. Incoming carrier currents, amplified by an incoming group repeater on panel 19, are fed to the channel filters such as 11, panel 22, whose output is demodulated by 20 Kc. current at 12, the resulting low-frequency current then passing to panel 21 where it is filtered at 13, further demodulated by 8 Kc. current at 14 filtered at 15 and amplified at 16. Corresponding elements 1<SP>1</SP> ... 6<SP>1</SP>, 11<SP>1</SP> .... 16<SP>1</SP> in panels 22, 23 appertain to the second channel. Spaces 39, 39<SP>1</SP> are empty in all such panels as 22 except one in which they are occupied by paralleling devices for the respective output and input channel filters. The central panel 20 includes test jacks, test sockets for measuring all the filament and plate currents, and alarm circuits (see Group XL (c)).