GB319712A - Compensation for phase variations on telegraph and telephone transmission lines - Google Patents

Abstract

319,712. Standard Telephones & Cables, Ltd., (Western Electric Co., Inc.). June 27, 1928. Transmitting sysfems.-Compensntion for phase displacement in currents transmitted on radio broadcasting systems, telegraph picture transmissions, television systems, &c., is effected by subjecting currents of two different carrier frequencies on the transmission lines to a third frequency which is low compared with the carrier frequencies, the low frequency component from each carrier frequency being selected at the distant station and differentially connected in order to indicate the amount of phase displacement produced and required to be corrected during transmission. It is shown in the Specification that for open wire lines, the amount of phase displacement produced with variations of frequency is a linear function. In one arrangement, Fig. 1, frequencies of 10000 and 5000 are transmitted from oscillators 0, O<1>, and a frequency of 250 generated at G is superposed thereon. Currents produced at the three frequencies are subjected to the phase displacement produced on the transmission lines L and at the receiving stations B, the higher frequencies are selected in respective circuits X, Y, the low frequency component of 250 cycles being selected from each of the higher frequencies and fed to oppositely connected transformer windings 10. A balance with normal line conditions is obtained, and the relative phase displacement produced by variations in line characteristics at frequencies of 10000 and 5000 is indicated on the meter 24. A relay 25 operates an alarm 26, and compensating phase adjustments are made on adjusters PA, PA<1> in the circuits X, Y. The adjusters may be mechanically connected or one instrument such as an adjustable condenser may be common to both circuits X, Y. In other arrangements, the separated low frequency components have normally a quadrature relationship and are supplied through thermionic rectifiers to a polarized relay controlling the operation of a reversible motor geared with the phase adjusters.