GB663397A - Multiplex telephone system having reduced band-width - Google Patents

Abstract

663,397. Telephone transmission systems. STANDARD TELEPHONES & CABLES, Ltd. March 4, 1949 [March 5, 1948], No. 5933/49. Class 40 (iv). A distributer 2, Fig. 2, cyclically connects n lines 1, 1, 1 to the transmission channel 3, and a further distributer 4 cyclically connects the channel 3 to n receivers 5, each receiver being fed through a network comprising (n-1) delay devices 6, 7 shunted by one-way conductors 8, 9 so that the signal is repeated n times to be substantially continuous. In a modification, a single delay device 14, Fig. 5, is used, and is shunted by a gating circuit 16 and an amplifier 15; the gate 16 is controlled by the distributer to be closed while the receiver is connected to the channel 3 so that when the receiver is disconnected the gate is open and the signal is repeated continuously. The three lines 1, Fig. 2, may be the output lines of apparatus which is fed with m signals, and shifts the frequencies of each of the signals so as to give a wide band in which the individual signals occupy adjacent frequency ranges, Fig. 4 (not shown). In Fig. 6, signals in lines 1 are all shifted in frequency, e.g. to occupy the range 4600 c/s. to 7700 c/s., and are " chopped " by a distributer 18; the pulses of variable amplitude so produced are translated into a five-unit code, and applied with other similar signals to the input of a distributer 19; at the receiver, a distributer 21 feeds the appropriate channels 2, where the five-unit code is transformed back into varying amplitude pulses by circuit 22, these pulses being repeated by circuit 23 (as in Figs. 1 or 5) and applied to distributer 24 for demodulation at 25. In a further modification, Fig. 7, the output from each distributer 27 is stored on the screen of an iconoscope 28, each row thereon comprising one pulse from each of the channels 1 ; by scanning these rows vertically, all the signals from each channel are sent consecutively so that the pulse from one channel only occasionally is adjacent to a pulse from another channel, thus reducing cross-talk. At the receiver, similar iconoscopes 32 operate in reverse to distribute the signals to the appropriate channels.