GB795699A - Improvements in or relating to telephone systems - Google Patents

Abstract

795,699. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Nov. 7, 1956 [Nov. 29, 1955], No. 34096/55. Class 40 (4). A pair of transformers in conjunction with a two-position switching device is arranged, in one position of the device to use the transformers individually to couple the two four-wire circuits together, and in the other position to operate as a hybrid transformer for coupling a fourwire circuit to a two-wire circuit. In the arrangement shown, with relay HCA unoperated, circuit AB from the switching equipment SE is coupled to circuit AB to the transmission equipment (e.g. carrier equipment) CE by windings 1, 2 and 5, 6 of transformer 1TRA, whilst coils 1, 2 and 3, 4 of transformer 2TRA couple the CD circuits. With HCA operated the two transformers are connected as a hybrid circuit for connecting a two-wire circuit AB(SE) to a four-wire circuit AB, CD(CE) the CD circuit on the SE side being connected by the switching equipment to a balance network. The arrangement is thus suitable for a " tail-eating " connection with another similar circuit as may be required for a connection completed through an operator's position (the respective CD circuits being interconnected with a cross-over). In either case the CD wires from SE are connected to relays RC, RD which may be used for controlling V.F. signalling. An arrangement with a slightly different arrangement of relay contacts and a built-in balance for the hybrid is also described, Fig. 1 (not shown).