GB869896A - Improvements relating to railway remote control systems - Google Patents

Abstract

869,896. Railway control systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Jan. 6, 1958 [Jan. 14, 1957], No. 1355/57. Class 40 (1). [Also in Group XL (c)] A railway remote control system comprises an oscillator or oscillators providing a plurality of output frequencies each of which will operate one piece of field equipment, means for coupling one or more oscillator outputs to a communication channel, the coupling being maintained substantially throughout the duration of the setting of the corresponding piece of equipment, and frequency-sensitive means associated with the equipment which is coupled to the communication channel but will respond only to the one particular frequency associated with that equipment. The oscillators include as frequency-determining element the combination of two mechanically-coupled tuned reeds or forks described in Specification 855,149. A plurality of such elements can be switched into a single oscillator (thermionic or transistor) or more than one oscillator can be provided. In Fig. 1, the oscillators Cof 1 , Cof 2 , &c. can be switched at will into the amplifier LA 1 , channel CH and amplifier LA 2 whence the selective receivers CR#1, CR# 2 , &c. respond to their appropriate frequencies and operate the equipment by relays C 1 , C 2 , &c. The switches IC 1 , IC 2 , &c. are then closed and connect oscillators IO# 5 , IO# 6 , &c. to the line, to indicate via selective receivers IR 5 , IR# 6 , &c. and lamps D 1 , D 2 , &c. that the equipment has operated correctly. Each relay C 1 , C 2 , &c. remains energized for as long as the corresponding switch S 1 , S 2 , &c. is made. The amplifiers LA 1 and LA 2 can be thermionic or transistor operated. Failure of any part of the system is detected by the circuit of Fig. 3, which uses a similar arrangement of two mechanically-coupled reeds 14, 15 as do the oscillators. The coil 14 is coupled to the channel CH, and as long as the corresponding frequency is present an output is obtained from the coil 15 which is rectified at 19 and operates the relay 18 to break the circuit at 17. The relay 18 is therefore energized intermittently and the device 20 will hold contact 22 closed only while the contact 21 makes and breaks continuously. If relay 18 should be held in either state the contact 22 will open and indicate a fault.