GB204185A - Improvements in or relating to transformer arrangements particularly adapted for high frequency telephony systems - Google Patents

Abstract

204,185. Western Electric Co., Ltd., (Western Electric Co., Inc.). Aug. 12, 1922. Relaying or repeating systems; wired wireless systems.-A double transformer arrangement used in a high-frequency telephony system forconnecting a single circuit carrying signalling currents in both directions to a pair of circuits in which signalling currents flow in one direction along one circuit and in the opposite direction in the other circuit; is characterized by the feature that the transformer arrangement acts also as a wave-filter. The incoming two-way single line L' is connected to the coils 2, 1 and 5, 6. The input side B of the four-wire circuit is joined to the coils 4, 3 and 8, 7, whilst the output side D is bridged by the coils 4, 3 and 8, 7. The main signalling currents flow in the directions indicated' by the full-line arrows. A balancing network N' is connected to coils 6, 5 and 2, 7. Series condensers 20 - - 23 are inserted across the inner ends of the coils contained in each of the circuits, and serve in conjunction with the inductance coils to form either a high-pass or low-pass filter, thus rendering unnecessary the use of excluding filters for undesired frequencies in either the line L<1> or the network N'. The impedance of the circuits are so balanced that no undesirable transfer of energy takes place between the input group D and output group B of the four-wire circuit, so that " singing " is prevented in that circuit. The four upper coils shown in the Figure are wound upon one core of the double transformer whilst the four lower coils are wound upon a second core. The induced and balanced potentials are indicated by the dotted-line arrows.