GB517036A - Multiplex multi-line carrier system - Google Patents

Abstract

517,036. Preventing inductive disturbance in multiplex carrier systems. STANDARD TELEPHONES &; CABLES, Ltd. July 15, 1938, No. 21076. Convention date, Aug. 18, 1937. [Class 40 (iv)] I n a system in which interference between par allel carrier lines is minimized by staggering the channel frequencies in neighbouring pairs, the voice frequencies from each of a number of gro ups of low frequency lines are brought by channel modulators 10 and 1st group modulators 20, 22, 24, 26 to the same frequency range from which they are then stepped down, with or without inversion, by 2nd group modulators 30 , 32, 34, 36. Correspondingly the incoming frequencies are brought to the same range and re-inverted if necessary by first incoming group modulators 31, 33, 35, 37 and are distributed to the appropriate lines with the aid of group modulators 21, 23, 25, 27 and channel demodulators 11. By this means only a. few different kinds of filter and a few high-frequency generators are needed. As shown, all the 1st group modulators for outgoing signals and the 2nd group modulators for incoming signals are fed with shifting current through the same filter 100 from a harmonic generator. The other group modulators are fed from the same harmonic generator in some cases directly and in others after a frequency shift by modulators 92 94, 98. Preferably the channel modulators and demodulators are rectifier bridges, connected as described in U.S.A. Specification 1,959,459, and the group modulators are of the type described in U.S.A. Specification 2,025,158, and suppress the input frequencies as well as the shifting frequency in their output circuits.