2008 CTs on 2012 IRSE tables

[PJW]

Thanks for your question; it illustrates why it is important to declare your railway's practices.

The attempt we were discussing here reflected:
UK mainline practice using Multiple Aspect Signalling,
implemented via Route Relay Interlocking / Solid State Interlocking.
In such a context, a "pres-set shunt" means that there is a GPL signal positioned partway along a main route and when the signaller sets the main route, the GPL is automatically cleared as a precursor to the entrance signal. The aspect of the GPL proves ALL the controls applicable the main entrance signal are satisfied and once it has cleared (and only then) does the main signal clear. This is done so that the driver on the main route does not pass the GPL displaying ON; note though that the route associated with the GPL as a shunt signal isn't set.

I think that the situation familiar to you is what we would call a preceding shunt and is how the locking would be arranged on a mechanical lever frame. In such a scenario the signaller first clears the shunt signal and then clears the main signal which reads over it and indeed there would be mechanical locking preventing that route from being set unless the GPL had already been set. Some relay based systems could implement the same type of logic and in such a scenario then you'd be right that the locking would be carried by the GPL and this used to summate and then get reflected in the main route. This is not UK mainline practice for colour light signalling; hence it would be WRONG IN THAT CONTEXT.

However it would equally correct to have answered an IRSE Exam question in your way IF YOU DECLARE THE RELEVANT RAILWAY WHOSE PRACTICE IT REPRESENTS.

So beware taking bits of information from one place and combining with bits from somewhere else as you can end up confusing different practices.
Learn one practice, stick to it and make sure to tell the examiner which railway it relates to.

I have a question of 124B(M). As it is already mentioned that preset of 126B is required before set 124B(M). Then why shall we consider the 152A(M), 156A(M), pt 242 status etc in 124 CT? I think those consider shall list in 126 CT weather in 124 CT.

Please comment. Thank you.

Looking at your Notes sheet first-



124B(M)-
You seemed to decide not to show as opposing locking 152A(M) on the basis that there is no overlap via 236R beyond 131. However the train can stop at 131 and the overlap will time out, releaseing the locking on 236. Still don't want to be able to set 124B(M) so that opposing locking was in fact needed after all. Similarly from 156 etc.

Same comment re the approach release using BG Q; since this is even further from the signal than the previous case, the opportunity for signal clearance and thereafter signal reversion is even more likely as things are at present on your CT.

Another thing is that the aspect should be proving that there is no premature release stored for 149; hence FH Q should be proved "not operated" and indeed any stick circuit or timer implementing the aapproach release of 149 should be down proved- similar to Raynes Park control (that is usually shown on NR control tables by $16 against the relevant track).

So pssibly just a few things to learn and tighten up on, but overall another set of CTs to be proud to have shared; I am sure that many other users of this website will gain from looking at your attempts.

I'll try to look at the points tomorrow.

Feedback and comments please?