GB546217A - Improvements in or relating to electric carrier wave signalling systems - Google Patents

Abstract

546,217. Repeating systems. STANDARD TELEPHONES & CABLES, Ltd. March 28, 1941, No. 4182. Convention date, April 3, 1940. [Class 40 (iv)] Each pair in a carrier cable carries three pilot currents, one for controlling the flat gain, another for controlling a slope network, i.e. adjusting the slope of the attenuation characteristic, and the third for controlling a bulge 'network, i.e. controlling the maximum amplitude of the attenuation characteristic without changing its shape, and it is arranged that if a pilot current fails, control of the element concerned is effected by the corresponding pilot currents of other pairs. In the arrangement shown, the pilot currents are filtered off at 23, separated in the anode circuit of a valve 26 and rectified by voltagedoubler-type metal rectifiers and the resulting voltages control the anode currents, which are derived in part from an A.C. generator 58, of valves 48, 69, 87. The output currents are fed in part to the heaters of variable resistance elements 10, 13, 16 associated respectively with the feed-back path of a flat gain amplifier and with slope and bulge networks and in part over resistances such as 60, 61 to control-buses such as 62 which are similarly associated with the pilot channels of other pairs. If, say, the pilot channel controlling resistance 10 fails, the resistance continues to be controlled over circuit 62 by the corresponding pilots of the other pairs. Specifications 469,667, [Group XIII], 508,341, [Group XL], and 540,844, [Group XXXVI], are referred to.