Improvements in or relating to telephone sub-sets

863,706. Substation circuits. STANDARD TELEPHONES & CABLES Ltd. Aug. 1, 1958 [Aug. 7, 1957], No. 24874/57. Drawings to Specification. Class 40 (4). A single non-linear resistance element is placed directly in shunt, without the use of an intervening transformer, with the transmitter, receiver, line terminals, or like-balancing network, the resistance of the non-linear element being dependent solely upon the voltage developed across a controlling resistor by the unidirectional transmitter-energizing current received at the line terminals. In the case in which the receiver is shunted, the circuit is the same as that shown in Figs. 2 and 3 of Specification 863,642 except that the arm of the bridge containing non-linear element 10 is omitted. Specification 706,785 also is referred to.