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My attempt at 2008 layout CTs
(17-08-2010, 09:23 AM)merlin89 Wrote: [ -> ]My attempt at 2008 layout CTs

Hi Merlin

I've gone through your control tables with a red pen - scan attached.

here are some general comments.

Overall, a very comprehensive attempt, with both quantity of tables and general completeness of controls acheived.

In many ways my comments are quite picky and trivial so should not be taken as critical; and indeed I may have made mistakes or missed things in a quick review. Also, I may have wandered off into personal preferences......!


I think your "timing to a stand" values are a little short -i find a good rule of thumb is 10s per 100m, plus 10s.

You need to think about why the (AA or AB) type construction is used where there is a pair of track circuits used for timing to a stand. Imagine that this could effectively be replaced by a single track circuit "AAAB":

if testing for track circuit occupied, "AAAB" would be occupied if either AA or AB is occupied - hence (AA or AB ) is a correct test for "AAAB" occupied.

if testing for track circuit clear, AA and AB must both be clear for "AAAB to be clear, hence (AA or AB) is not the correct test - the standard ...AA, AB ... list (where comma means AND ) is correct.

Also need to think about how far your square bracket extends to allow still-occupied approaching sectional route locking to be conditioned-out by the timing to a stand conditions. I have shown my preference, but different interlockings may do this differently.


Points 254

The extra TC clear conditions I have added in the dead locking are foul track circuit conditions - easily missed, possibly good for some marks.Also for 233.

The swinging overlap condition has been spotted and well addressed.

These points are trailing in the swinging overlap of route 147C(S) - hence the extra entries. As trailing points, the full "swinging overlap requres" columns are not used.

254N do not provide any flank protection to routes 166A(s) or 161A(M). the only need to call 254N if these routes are set is to ensure that if a route is set up to 157 signal, it will not be prevented from setting by 254 points being locked R by a train occupying CH on route 166A(s) or 161A(M). Hence it is excessive (but not wrong!) for these routes to lock 254 points N.

124B(M)

Notice that 126 signal is preset by this route.

Since FHQ is used for approach release of the signal ahead, and it could have been falsely operated previously, it is necessary to prove the treadle not operated before signalling up to 149. (Raynes Park control). You don't often see this on "real" control tables because this use of treadles is a peculiar preference of IRSE exam plans!.

147B(s)

if you're timing to a stand an opposing direction move which is itself permissive, you have to consider that, by definition, the "track occupied for time" condition would be true before an opposing move set out - therefore you cannot use this to prove that move complete. An alternative is to time the previous track clear (for the same time value) as shown for 164B©


I hope the above helps - keep up the good work.


Reuben

Many thanks Reuben will review this weekend
I have had a go at this paper and it seems i have made similar errors. I can't see your attachment though Reuben, would it be possible for you to make it available?

Thanks,

Priyank
(18-09-2010, 10:46 PM)priyman Wrote: [ -> ]I have had a go at this paper and it seems i have made similar errors. I can't see your attachment though Reuben, would it be possible for you to make it available?

Thanks,

Priyank

Priyan,
Have a look at this thread
http://www.irseexam.co.uk/showthread.php?tid=135
In there are model answers for the 2008 layout from Reuben and myself, but there may be typo's as they were never checked.
If you post them I'll try and have a look, running AST this next week tho
Mark