Patent GB-375450-A (GB)
Title: Improvements in or relating to electric signalling systems and apparatus
IPC: G08B25/08
Filed: 1931-04-01
Abstract: 375,450. Electric signalling systems and road-traffic signals. GRASEBY, R. C. and MATTHEWS, S. J., Kingston By-Pass Road, New Malden, Surrey. April 1, 1931, No. 9871. [Classes 40 (i) and 118 (ii).] In an electric signalling system a signalling apparatus, e.g. an audible signal apparatus, is connected to a local source of power by a relay responsive to a particular frequency, the frequency being applied to the system at predetermined intervals to actuate the signal a number of times. In addition a second signalling apparatus, e.g. a visual signal apparatus, is connected to the local source of power in response to receipt of current of this frequency and is disconnected on the receipt of current of a second frequency, the connection being maintained by a mechanical locking device. As described, the invention is applied to a system in which signals are given to indicate, to police and traffic, that fire engines are to be expected, the audible signal indicating the number of engines, and if illuminated traffic control signals are used, all the controls are altered to the " stop " indication. Referring to Fig. 1, the apparatus 4 is situated at the fire station and controls signals over routes 19, 20, and 21. A motor 1 drives generators 2 and 3, which generate current of 16.7 and 100 cycles respectively, and also drives discs 14 .. 17 which carry teeth 18. The wheels 14 .. 17 control contacts 9 .. 12, the contacts being made respectively one, two, three or four times in succession and are used to indicate the number of engines to be expected. If, for example, two engines are to pass over route 19, switch 5 is moved into its upper position and switch 13 is connected to contact 10. Current of frequency 16À7 cycles is repeatedly connected to route 19 twice in quick succession. Relays 24 and 31 at the distant point respond, relay 31 locking to connect current to visual signal 23 and relay 24 ringing alarm 22 at each pulse. To remove the signal, switch 5 is moved into its lower position to connect generator 3 to the circuit. Relay 41 responds to this frequency and unlocks relay 31. Relay groups 56, which are similar to relay groups 31 and 41, provide, through lamps 55, a local check on the route over which the signals are being transmitted. The route 21 connects with an illuminated traffic control signal and the relays 31 and 41 control relays 54 which, when energized, alter all controls to the " stop indication. As illustrated in Fig. 1 the construction of the apparatus fitted at the signal points is that described in Specification 367,433 but the alternative construction illustrated in Fig. 2 may be used. The relay 24 controls springs 30 which are in the circuit of the audible alarm. The visual alarm is controlled by relays 31 and 41. When the operating pulse is received relays 24 and 31 respond, relay 24 releasing when the pulse ceases. Relay 31 closes the visual alarm circuit at 36, 37 and also closes contacts 50 in the circuit of release relay 41. The projection 40 on the armature 32 slips under the notch 46 on bell crank 45, which is pulled to the right by spring 44 when relay 31 operates and the armature 32 is locked in operated position. The movement of 45 to the right allows springs 52, in the circuit of 31, to open. When the releasing frequency is received, relay 41 pulls up and allows 32 to move back under action of spring 34. Springs 50 break the circuit of 41 and 45 returns to its normal position. Condenser 47 is connected in series with relay 41.