Automatic Signalling

Another promising German development of the selenium cell in railway service, making automatic signalling possible even where steel sleepers are employed, is known as the Hampke arrangement, employing the so-called “point” or intermittent system of signalling. Previous arrangements of automatic signals without track circuits possessed no sure automatic means of indicating when a train with all its vehicles complete had passed out of the block section. Hampke's apparatus solves this problem by an arrangement which makes it possible to observe the passage of the tail end of a train past a fixed location. The arrangement calls for a tail light detector consisting of a lamp bulb throwing an intense concentrated ray of light on to the train, and a selenium cell forming part of the circuit of a line relay. A special mirror is fitted to the red tail light of the train, this mirror being similar to that employed in the Baseler apparatus. Immediately the rear of the train passes the selenium cell detector, the mirror directs the ray of light back into the selenium cell and renders it conducting, so that the circuit through the relay is closed.—(From Our London Correspondent.)

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