GB224280A - Improvements in submarine telegraph systems - Google Patents

Abstract

224,280. Western Electric Co., Ltd., (Western Electric Co., 'Inc.). Aug. 3, 1923. Duplex telegraphs. - A method of signalling over a long continuously loaded submarine cable consists in simultaneously transmitting in opposite directions two trains of signals having different transmission frequencies, one train being transmitted as a series of impulses and received with amplitudes substantially greater than ordinary extraneous disturbances, and the other being transmitted as a modulated wave train and received with amplitudes of the order of, or less than, such disturbances. The cable 1 terminates in duplex bridges having the usual blocking condensers 2, 2<1> and artificial lines 3, 3<1>. At one end is an automatic transmitter 4 which sends direct current signals composed of impulses of a variable length, spacing and polarity, and occupying, a low frequency range. At the other end is a transmitting key 5 for sending wave trains generated by an alternator 6, these signals being, in a higher frequency range of from 75 to 300 cycles per second. The direct current signals are received through a low-pass filter 11, a combined amplifier and shaping network 12, and a recording device 13, the filter 11 eliminating the disturbances created by the transmission of the high frequency signals. Signals sent by the key 5 are received through a transformer 7, a high-pass filter 8 for eliminating low-frequency signals, an amplifier 9 and telephone reeivers 10. Artificial lines.-The artificial lines 3, 3<1> are balanced with particular care for the high and low frequency signals respectively.