194904 – Woolley – Testing Maintenance of A.C. Relays

The constantly increasing application of electricity to Railway Signalling necessarily requires a large number of relays of various kinds. Today, 2,500 polyphase and 3,500 vane relays are used in connection with the signalling of the Melbourne Suburban Railway System. The present trend in signalling is to- wards the greater use of relays in lieu of other types of apparatus. For instance, the searchlight signal, the mechanism of which can be considered as a relay, is gaining in favour and superseding previous types of signals. Likewise, relay and circuit interlocking which permits speedier setting up of routes is superseding mechanical locking between levers with its necessary electric lever locking.

From almost all points of view, relays form the most important apparatus in railway signalling, and it is, therefore, appropriate that we should consider the details of regular testing and inspecting, together with periodic overhauling which is essential for their satisfactory functioning.