GB198011A - Improvements in multiplex transmission systems, particularly submarine cable systems - Google Patents

Abstract

198,011. Western Electric Co., Ltd., (Western Electric Co., Inc.). Feb. 15, 1922. Wired wireless systems. -In a multiplex transmission system, particularly for a submarine cable, having a plurality of transmitting and receiving channels associated with the transmission circuit, each transmitting device is connected to points neutral with respect to the receiving devices. As shown, each transmitter is connected to the midpoints of a balanced transformer, the arrangement being distinguished from known arrangements in which a single balanced transformer is used for all the channels. The invention is described with reference to a submarine cable system in which the circuits are extended from the shore station of a grounded cable SC, through metallic circuits C. Ci, to a distant central office, provision being made for telephone, high-frequency carrier, and direct current signalling. Extension C is connected through a transformer T and is provided with branches BL<2>, HL<3> each including transmitting and receiving channels. The transmitting channel TL2 is connected to the midpoints of a balancing transformer 12 through which the receiving channel RL2 is associated with branch BL2. Vacuum tube or other amplifiers TA2, RA2 are provided and also band filters TF2, RF2, adjusted to transmit voice frequencies of, say, 275 to 2300 cycles, so that the branch may be used for telephone purposes without interference with other channel. Similarly a transmitter SR3 is connected to the midpoints cf a balance transformer 13 through which a receiver RR3 is associated with branch BI3. A transmitting amplifier TA3 and receiving amplifier RA3 are provided and also band filters TF3, RF3 adjusted to transmit carrier frequences outside. the telephone frequency range. Other carrier frequency channels may be similarly connected, the filters being adjusted to secure selectivity for different frequencies. Extension C1 connected to the cable leads to a direct current signalling channel BL1 and includes a retarding coil 20 to prevent shunting of the telephone and carrier currents, and a similar coil 21 shunted by a capacity 22, the whole forming a filtering arrangement freely transmitting low-frequency DO signals. RR, is a fourwinding differential receiving relay of known type, controlling an auxiliary relay RR1, which in turn controls the receiving channel RL1. The transmitting relay SR1 sends positive, or negative impulses through a. filter 23, 24 to the midpoints of relay RR1. Relay RB1 is connected to a balancing network TN1. Filter 21, 22 a balanced by a similar arrangement 21<1>, 22<1> whilst coil 20, transformer T and extensions C, C, are respectively balanced by 20<1>, T<1>, N, N1, the cable SC being balanced by an artificial line SN.