Power-operated doors on multiple-unit electric railway stock

The paper refers briefly to the development of power-operated doors on multiple-unit electric stock from the system of manually-operated gates used on the early ¿tubes¿. Systems of door control are discussed, with particularreference to protection against irregular operation, and particularsare given of the special types of door-control magnet valves developed by London Transport and adopted for certain BritishRailways electrification schemes. Compressed-air door-operating engines are similarly described, with a reference to methods of ¿controlling¿ the door movement and arrangements for the detraining of passengers in emergency. Some principles governing the design of door ¿proving¿ circuits are stated, with a mention of recent developments in the detection of door obstruction or faulty operation of the equipment. The concluding Sections refer to a new type of key-operated door controller, to experimental exterior door-control mechanism designed especially for operation by a guard located at the centre of a train, and statistical evidence of service reliability.