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The New Zealand Railways Magazine, Volume 3, Issue 2 (June 1, 1928)

Interesting Electrical Problems

Interesting Electrical Problems.

Many interesting problems calling for expert technical investigation to-day face the signal engineer, and there is a big field for the perfection and improvement of existing apparatus, and for the development of new equipment calculated to prove of utility in meeting the exacting demands of modern railway operating. In his recent presidential address to the Institution of Railway Signal Engineers, Mr. W. S. Every, Signal Engineer of the London Underground Railways, reviewed thoughtfully the many problems associated with modern train signalling. The rapidly increasing use made of electricity in railway signalling, Mr. Every remarked, undoubtedly tended to make increased demands upon the knowledge and intelligence of all employed in this branch of railway working, and it was essential that the modern railway should run efficient schools for the education of their signalling staffs. The increasing use of costly automatic plant to eliminate the human element in train signalling was most marked, and railways the world over were doing a great deal in this direction.

Regarding the utilisation of electricity in train signalling, the query was raised as to what are the relative advantages of alternating current and direct current for signalling purposes. One easily recognised the advantage of alternating current for the main signal supply, but the question related more particularly to the actual operating circuit. Thanks to the development of rectifiers, it was now simple to obtain a direct current supply from alternating current mains, and where there was no electric traction, direct current apparatus could be used with advantage on account of its simplicity of design and lower cost. With the increased use of light signals, however, alternating current was to be preferred owing to the ease of transforming to the low voltages required for the lamps. A serious attempt, it was rightly stated, should also be made to recommend standard operating voltages for signal apparatus, both alternating current and direct current, and the range of voltages should be reduced to a minimum.