Re: another cityrail signalling question

[Stuart Ellis <festy@terrigal.net.au>]

David Johnson

     While I was looking over the ausrail newsgroup archives for April,
I found you and others were trying to work out what those gray boxes
between the tracks are at Wynyard.  They are called a D.P.U. short for
detection point unit. Yes you were sort of right it does consist of an
induction coil. It is placed against the side of the rail and allows the
wheel to pass it, in turns causes the induction coil to react and
operate a relay.  It replaces the need for excessive use  track
circuits. i.e. your overlap tracks. As you are aware I was a qualified
signal electrician, and if you have any queries in future, please don't
hesitate to drop me a line

Stuart Ellis.