(10-03-2010, 01:17 AM)interesting_signal Wrote: Thanks for such detailed feedback. I've gone through the questions you posed, and the answers are attached. I already realise some things I've done wrong, and will try and correct these. I'll also be resubmitting control tables for 144A(S).
I found your responses illuminating- perhaps some will act as a prod in the right direction for you to relook at some of your CTs, some confirmed my suspicions whereas others negated other working assumptions.
a) You do need to declare this in your exam answers; in your case it is looking like "Railtrack, mid 1990s, free wire Route Relay Interlocking".
a) & b) Your wider experience will be useful for the written questions but could perhaps confuse re the Control Tables slightly if you muddle practices- though so far this does not seem to be a problem. You have good source material but be aware that you will find some discrepencies between them, as all to slightly different standards. If you actually UNDERSTAND this is not a problem, but it can be tough in the initial learning phase.
c) see later
d) and e) Perfectly correct understanding- issue is that you didn't seem to be following it; I thought that it was this which was misunderstood but evidentally it is something else. Also be aware that we do often bracket expressions together when they span across various columns, often where there is a wide space then we link by filling the interim space with a dashed line: viz - - - - -
[Another comment re the maintained locking; ideally you should have horizontal lines dividing up into different levels the 3 associated boxes in order to keep the expressions together; sometimes where there were multiple routes the entries became a bit out of kilter with the list of tracks. It is a pain to do this in Word though, so perhaps use dashes to "join" and so it is obvious when you need to leave a line gap so that the two (or three if timer) column entries align correctly]
f) correct but doesn't match your CT
g) correct. You cannot actually tell which route / routes the "Auto" applies to. Actually generally only to one, but can be multiple. Probably would apply to both A(M) and A(W). Never to a © or (s).
h) correct but it MIGHT stop anywhere along the platform (e.g. if it is short train and the passenger station entrance is in the middle or one end of the platform to make it convenient- hence could stop short of DB track. Note that once train has come to stand it has no permission to restart unless the platform starting signal has been cleared or a verbal instruction from signaller.
i) similarly it may stop anywhere short of the first train; if due to join then will approach very close (3m) , stop and then when authorised move forward to couple. If not due to join will stop futher away if room permits. In this case given lengths. yes almost certainly on DC
j) Perhaps my question wa poorly worded; what I actually meant was "how does the MEANING of the aspect differ to the driver"
k) Good answer- practically never as it will always be one or the other; as I think you have realised yoour CT entry was a bit nonsensical in this respect. However there is an unusual scenario in which allowing a point movement to complete is a sensible control, but that is for the very advanced course!
l) Correct and I think you realise what I was getting at
m) Correct; the issue is that you need to learn to read IRSE diagrams re the assumed position of the clearance point. This sort of also explains item c); you know about foul but hadn't recognised the layout depiction for what it was.....
The trick is to look at which parallel running lines are at the nominal 6ft spacing (e.g. Up and Down Main) and then can assume that any IRJ which is closer to a point tip than opposite the other end of the crossover is bound to be foul- hence in the case of 207R this means both BM and EH. Where ther is reason to assume wider spacing (e.g. there is a platform separating the Down Loop and Up Loop) then IRJs opposite the switch toes of the other end of the crossover are bound to be well clear- for example I would assume that the BH/DA joint position would be clear of both and Up Loop (not that it matters since points are numbered 203A and 203B)
The answer to c) should be "ED locks 203 from going Reverse unless 205 is detected Normal since ED is a conditionally foul track circuit; also even if the joint had been at clearance there is also route locking after 115A"
n) Nothing needs to be said.
I certainly found this exchange useful in clarifying where you are coming from- being open about what you do and don't understand makes offering appropriate help much easier for me, so well done!
PJW