The New Zealand Railways Magazine, Volume 2, Issue 6 (October 1, 1927)
In a branch of railway activity such as train signalling, where refinements and changes in operating practice are constantly being introduced, the need for an educational establishment such as this is very real. Reviewing recent developments in the realm of signalling, it would seem that what is probably the most promising experiment is the employment of intermittent or transient track circuits. In his presidential address to the Institution of Railway Signal Engineers, Mr. E. F. Fleet, of the London and North Eastern Railway, made interesting reference to a system of this character installed on a section of single line at Castleford, in Yorkshire.
In the Castleford installation continuous current track circuit is dispensed with, but before a train can be signalled in either direction, the transient impulse current must have swept the track from both ends, first by the signalman offering the train, and then by the signalman accepting the train. In each instance the energising of the circuit is dependent upon the line being clear and opposing signals being in the danger position.