By-pass apparatus for signalling systems in which carrier current signalling is effected over low frequency signalling circuits

摘要

502,814. Multiplex transmission. STANDARD TELEPHONES & CABLES, Ltd., ROSEWAY, W. N., and WRIGHT, F. C. Sept. 24, 1937, No. 25950. [Class 40 (iv)] A low-frequency line to which are connected a number of wayside stations is employed for high-frequency signalling, each wayside station being byepassed by a high-pass filter HPF. The low-frequency apparatus at each station is connected between two parts of a low-pass filter LPF which can be connected, by switches SW1, SW2, to the line or to an artificial line CN.