Patent GB-479884-A (GB)
Title: Improvements in or relating to electrical signalling systems
IPC: B66B19/06
Filed: 1936-08-14
Abstract: 479,884. Electric signalling systems. AUTOMATIC ELECTRIC Co., Ltd., (in Liquidation), McCABE, F., and SAVILLE, W. Aug. 14, 1936, No. 22467. [Class 40 (i)] A Wheatstone bridge is used to indicate the origin of a call in a mine haulage signalling system, the initial call causing two lamps of two groups of lamps to light, one of which is extinguished by hand so that it can be relit by the second signal to indicate that the two signals are given from the same section of the track. The signals control the lamps only if they are of long duration so that the system can be used for transmitting messages by using signals of short duration. When a stop call is made the signalling lines, which are joined to terminals 11, 12, are connected together for an appreciable time. Relay L responds and if the call is in the nearer half of the haulage way marginal relay M also pulls up. The signalling bell is operated over line 10, relay TD is energized and relay M locks. Relay MA pulls up if relay M has energized. Relay LA energizes to connect up the Wheatstone Bridge and magnet WM steps wipers W. The resistance in the adjustable arm of the bridge comprises the resistance connected to banks W3, and W7 if relay M has energized, line relay L and the resistance of the line to the point of connection and the resistance of this arm is gradually reduced as wiper W3 steps. When the wipers are on the terminals associated with the calling section of the line the current flow through relay BR is reversed. The relay BR operates to stop the switch and relay MW pulls up. The white lamp associated with the section is lit over one of the wipers W1, W4, W5. The line is divided into 50 sections and relay M is adjusted to operate on sections 1 ... 30 of the line so that lamps 26 ... 30 can be lit over either W4 or W5 depending on whether M has pulled up or not. This reduces the steppng time of switch W, but if the time to make 50 steps is not considered to be too long for a signal pulse, relay M and wiper- and bank W4 need not be provided. Switch R now steps until its wipers are in positions corresponding to wipers W when relay CR energizes. Relay RM pulls up to light the associated red lamp over wipers R1, R4 or R5. When the signal pulse ceases relay L falls away followed by TD and LA. The attendant, having stopped the haulage motor, releases relay MW by throwing key WCK so that the white lamp is extinguished and switch W homes over off-normal contacts ONW. The red lamp remains lit and relay POA energizes and locks to off-normal contacts ONR. The start signal comprises 2 long pulses. On the first pulse relays L and TD pull up but the circuit of relay LA is held open by relay POA. On the cessation of the pulse relay L falls away before relay TD allowing relay PO to energize and lock. On the second long pulse relays Land TD pull up as before and relay- LA can now operate to recomplete the bridge circuit and to complete the stepping circuit for magnet MW. The bridge is adjusted as described above and a white lamp is lit as before. If this lamp corresponds with the glowing red lamp, the operator knows the call is from the same point on the haulage way and the motor can be restarted. The apparatus restores to normal when both keys WCK, RCK are operated. The apparatus can be used for normal bell signalling if the pulses are all short, relay L operating to ring the signal bell over conductor 10. Spark preventing equipment of the usual type may be provided. The visual indication could be repeated as an audible code by suitable connections from the R switch.