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The New Zealand Railways Magazine, Volume 3, Issue 10 (May 1, 1929.)

Latest Signalling Developments

Latest Signalling Developments.

Inventions by the thousand have been patented in recent years aiming at the simplification and betterment of train signalling systems. A few of these patents have been found of real utility: an immense number have been tested and proved impracticable under modern service conditions. After almost every mishap on the line there arise wiseacres innumerable to point out alleged defects in present-day railway signalling methods; but it is nevertheless a fact that, all things considered, there could hardly be devised safer and more reliable systems of train movement than those favoured by the leading railways of the five continents. Now and again some inventive genius comes forward with really good ideas for the improvement of signalling equipment, and a genuinely sound idea of this type is quickly snapped up and brought into service.

A most promising avenue of research at present being explored concerns the employment in signalling of the metal selenium, which is peculiarly susceptible to the effects of rays of red light. Following the discovery that the projection of red light rays on to the metal enabled the transmission of an electric current corresponding to the intensity of the rays, a series of elaborate experiments associated with the utilisation of selenium in train signalling, were commenced, some three years ago, by the German railways. Having carried out these experiments, the German authorities have fitted up a section of track in the Munich area with special signalling apparatus, employing concave mirrors on the signals and spot lights and sele-nide cells on the locomotives, by which the rays of light are converted into electric oscillations regulating the locomotive brakes according to the signal indication. A test of the apparatus, as fitted to a miniature railway system, has also recently been made at Home by the London & North Eastern Railway, but, for the time being, the whole device is in the experimental stage. That much will be heard in the near future regarding developments of the type indicated, appears certain. Meantime, it is worth noting that the London & North Eastern Railway are at present experimenting with selenium cells in another direction, namely their use for the automatic lighting and extinction of passenger carriage lamps on entering and emerging from page 19 tunnels. Across the Channel, the possibilities of selenium are being closely watched by the Paris underground railways, and, very shortly, experiments are likely to be made by this important transportation system in the selenium signalling apparatus.