GB259546A - Improvements in methods of reducing noise in telephone circuits - Google Patents

Abstract

259,546. Standard Telephones & Cables, Ltd., (Assignees of McCurdy, R. G.). Oct. 7,1925, [Convention date]. Two-way repeating systems ; induction, preventing and minimizing; phantom-circuit systems.-To reduce noise in systems in which a number of four-wire circuits run in a multiple cable between repeating points, the circuits are drained at points where the power level is comparatively high, e.g. at the output of the repeaters. This is effected by grounding the midpoint of an impedance connected across each circuit. In the system described the circuits are grouped in pairs and phantomed. The mid-points of the line sides of the phantom output transformers are grounded as at 5 in repeater E. This drains the side as well as the phantom circuits. The incoming circuits are not drained, but draining the others, which occupy the outer positions on the cable, has a shielding effect on them. At a point between repeating points at which the power level on both sets of quads becomes equal, they are transposed, the W-E circuits occupying the outer positions from this point to repeater W at which they are drained as at 7.