GB548473A - Improvements in 4-wire terminating arrangements in electrical communication systems - Google Patents

Abstract

548,473. Repeating and multiplex translating systems. STANDARD TELEPHONES & CABLES, Ltd. (International Standard Electric Corporation). July 26, 1941, No. 9520. [Class 40 (iv)] Hybrid coils are avoided at the junction between a two-way two-wire path and two one-way paths by the provision of a reversiblemodulator in the two-way path and filters appropriate to the respective side-bands in the one-way paths. The principle is applied to the termination of a four-wire repeating system, Fig. 1 (not shown), to the two sides of a two-wire repeater, Fig. 3 (not shown), to a system with one voice frequency and one carrier channel, Fig. 4 (not shown), for coupling the low frequency and high-frequency lines to the frequency changing arrangements, and to multiplex carrier systems, Figs. 5 and 2. In the arrangement shown in Fig. 5, speech currents from a number of telephone lines are spread in a first modulator stage over a range from 60 to 108 KC. and this range is passed through a reversible modulator MOD-G, the lower side-band being used for the outgoing line. The incoming currents cover the same range but are brought by a modulator MOD-R to the range corresponding to the upper sideband and then by MOD-G to the range 60- 108KC. In the arrangement shown in Fig. 2, identical reversible first modulators, individual reversible second modulators such as MOD 1-2 and individual receiving modulators such as MODR-1 are provided.