GB234338A - Loading coil cases for transmission systems such as telephone systems - Google Patents

Abstract

234,338. Western Electric Co., Ltd., (Western Electric Co., Inc.). Sept. 8, 1924. Inductances.-In a four-line telephone or like transmission system comprising two side circuits and a phantom circuit provided with loading coils for each circuit, a separate inductance of a magnitude calculated to reduce side-current to phantom-circuit cross-talk is connected in each of the line windings. In the loading unit shown in Fig. 2 the loading coils 10 for several quads are mounted on hard wood spindles 11 supported in bosses 12 in the bottom of a cast-iron casing 7 having a flange 8 to receive a cover. The spindles 11 are clamped at the top in a spider 13 fastened to the casing. A terminal board 14 of hard wood mounted above the coils is provided with sockets to receive the correcting inductances 16. These are chosen after measurement of the cross-talk between each phantom-circuit and its side-circuits. They are wound on straight cores of silicon steel or iron dust material and are arranged on the board 14 so that there is substantially no magnetic linkage between them. Small non-inductive resistances may also be mounted on the board 14 and connected in the opposite line to that in which the inductances 16 are connected to balance the resistance thereof. Fig. 3 shows the connections for a single quad 24 to side circuit loading coils 21, 22, phantom circuit loading coil 23, balancing inductances 16, 16<a> and balancing resistances 17, 17<a>. The connections to the loading coils from the cable are taken through a central opening in the board 14 and those from the coils to the balancing devices between the board and the casing. Specifications 103,188 and 235,053 are referred to.