GB147756A - Improvements in telephone and the like systems - Google Patents

Abstract

147,756. Latour, M. May 23, 1919, [Convention date]. Repeating and amplifying systems; thermionic repeaters; induction, preventing and minimizing. -In a telephone or like system, an amplifier at an exchange has its input circuit connected to a subscriber's line, and its output circuit to a trunk line, so as to amplify signals passing from subscriber to trunk line. Signals coming in on the trunk line do not pass through the amplifier, but through a transformer to the subscriber's line. Artificial lines are connected both in the input and output circuits, with balanced connexions to prevent the amplified outgoing signals from affecting the subscriber's line and the input circuit of the amplifier. As shown in Fig. 1, one of the terminals 12 of the subscriber's line is connected through an artificial line 13 and the secondary coil of a transformer 10 to the other terminal 12. The primary coil of the transformer 4 feeding the grid circuit of the valve 1 is connected between one terminal 12 and an intermediate point on the coil 10. The secondary coil of the output transformer 7 is connected across the trunk terminals 8, one connexion including an artificial line 11. The primary coil of transformer 10 is connected between one terminal 8 and an intermediate point on the secondary of the transformer 7. The transformer 10 may be replaced by an auto-transformer or by a resistance coil.