Patent GB-535440-A (GB)
Title: Improvements relating to electric remote control systems
IPC: B61L7/08
Filed: 1939-12-21
Abstract: 535,440. Electric signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Dec. 21, 1939, No. 32690. Convention date, Feb. 17. [Class 40 (i)] [Also in Group XXXIX] In an electric remote-control system of the' type in which a number of field stations are selectively controlled from a control office over a common set of line wires an'additional independent voice frequency communication channel, e.g. for telephony or selective control of a subsidiary system is provided and the line relays of the selective system are arranged to function as loading coils for the telephone channel. As shown the invention is applied to the centralized traffic control system described in Specification 415,787 wherein selective control and supervision of a number of outlying stations is effected over a pair of line wires Y, by'Z coded time-spaced D.C. impulses under the control of relays OT, OR; T, R; at the respective stations (Fig. 1). Codes are transmitted from the outlying stations for supervising the condition of apparatus, the relay at the signalling station being energized to isolate the station more remote from the control office. In order to improve transmission sensitive line relays of the biassed polar type are used instead of the neutral relays and in the system described in Specification 415,787 and a shunt 6 and chokes 7 are provided for discharging the line during transmissions. Two winding line relays R are employed as loading coils and low- and high-pass filters 8, 10 are provided. As shown in Fig. 1 the voicefrequency circuit extends from the telephone equipment 9 at the control office through high-pass filter 10, relays R and back-contacts of relays M to equipment 9 at the end-station. When an intermediate station is transmitting the voice-frequency circuit is maintained intact by condensers 11 across the contacts of relays M. If the stations are irregularly spaced the electrical equivalent of uniform spacing to eliminate reflection losses is obtained by condensers 12 or loading coil 13. Line relays of the ordinary neutral type may be employed relays at alternate stations being connected in the respective lines in order to balance the line system, Fig. 2 (not shown)'. Additional channel control subsidiary system, Fig. 3. The system comprises stations O, IS- 35S, on one line section controlled by units OTA, ORA, and R, M, E, T, and stations 36S-70S on a separate line section controlled from station O over an A.C. channel to station 35S acting as a repeater converting from A.C. to D.C. Station O is provided with A.C. transmitting and receiving equipment OTB, ORP associated with the line over a hybrid coil 15, the transmitting source being represented at BX1, CX1. The repeating equipment at line terminal 35S is also associated with the line over a hybrid coil, received signals being passed over timed circuit 17 and rectified at 18 to control relay OTP which repeats the signals in D.C. form over the second line section. Signals in the opposite direction are repeated by line relay ORB which connects up A.C. source BX2, CX2 preferably of a different frequency. The system may be extended to control further line sections by using additional control channels.