GB247612A - Improvements in electric amplifying apparatus - Google Patents

Abstract

247,612. Kirkland, J. W., (Allgemeine Elektricitõts-Ges.). Aug. 21,1924. Two-way repeating systems.-In a two-wav repeater, reaction between the input and output circuits of the amplifiers due to differences in the impedances of the real and, artificial lines is prevented by the insertion in each speech current path of chokes the impedances of which are varied in accordance with the direction of speech, by an alteration of the magnetization of the choke cores brought about by rectifying part of the speech currents and passing the resultant direct currents through additional coils wound on the choke cores. Fig. 1 shows a two-way repeater comprising speech amplifiers R1, R2 and artificial lines Kl1. Kl2 for each direction. Choking coils Dr1, Dr2 for each direction are preliminarily magnetized over one of their windings. Speech currents arriving over the line F1 pass to the speech amplifier R1 and through the choke Dr1, which owing to its pro-magnetization has no choking effect upon the speech currents. A portion of the amplified speech currents passes to the rectifier R2<1> and thence to a coil on the choke Dr2 the magnetization of which is reduced and its inductivity increased to cause it to choke out any return currents through the amplifier R2. The rectifiers R1<1>, R2<1> are adjusted, so as to be uninfluenced by unamplified speech currents. In a similar manner a portion of the amplified speech currents coming over the line F2 is passed through the rectifier R1<1> to increase the inductivity of the choke. Dr1. According to a modification the cores of the chokes are not premagnetized and normally the chokes have a high inductivity and exercise a choking effect. During speech a portion of the speech currents is passed before amplification through a rectifying amplifier and thence to a coil on the core of the choke in the speech path, thereby reducing its inductivity and permitting the speech currents to pass. Back-coupling currents, however, are throttled by the choke in the return path.