GB295017A - Improvements in or relating to remote control systems - Google Patents

Abstract

295,017. Associated Telephone & Telegraph Co., (Assignees of Nelson, M. L.). Aug. 6, 1927, [Convention date]. Switching systems.-Switches or other apparatus located at comparatively short distances from a control station are operated and supervized over separate pairs of conductors of which one of each pair may be common to all. Direct current is sent in either of two directions to close and open a switch and alternating current is applied to the conductors by the closed switch to operate a supervisory signal. A change in the position of a switch which is not caused by the operator operates an alarm and a visual signal which identifies the switch; the visual signals may be lamps or relays. A key K is raised or lowered to send current in one or other direction from battery B through polarized relays 9, 24 in control and sub-station respectively, over line wires 22, 23, the latter wire being individual to the switch CB to be operated. A self-centering relay contact 25 is thus moved to actuate one or other relav 28, 29, thereby energizing closing or opening coil 32, 33 of the switch. Simultaneously contact 10 of relay 9 is set on contact 11 or 12. When the switch CB is closed an auxiliary contact 35 completes a circuit including an a.c. source such as 37 and a low impedance-relay 14 which operates a contact 15 to light one of the lamps 6, 7. The circuit of a relay 18 closes when the switch CB again changes its position, unless this is due to operation of the key K, owing to the operation of contacts 10 and 15. The relay 18 when energized lights a white lamp 8 and rings an alarm 21. Operation of the key K to reset the switch CB clears the alarm signal unless the switch fails to respond due to a fault. A similar system is also described in which relay indicators replace the lamps.