Answers to 2003 Part A Q1 & Q2

[PJW]

Referring to
"3.You didn't declare your standards"
So could I use NR standard? The difficulty is I have never seen these standard, how could I know which one I am using.

I do understand difficulty. IRSE would say "You are a signal engineer- just follow the standards to which you normally work. You must know these; we will undertake to mark you according to them- this is IRSE examiner problem, not yours".
However I agree that there are many signal engineers (including in the UK) who don't "signal the layout" or "do Control Tables" in their job; sometimes not even in their company. This creates difficulty and hence this is why most people adopt NR standards; however these are one railway company's standards and are not readily available; many of us have access to them but they are not ours to distribute. However of you look at most of the discussion / examples on this website then tend to average to the early 2000's NR practice; sorry but it is the best I can do.
I think that some in IRSE exam committee are beginning to think upon this issue and whether there should be any greater amount of standarisation of practice and Control table presentation to suggest that candidates follow as a default in the exam if they are otherwise unclear......

Referring to 4.Opposing route locking:
There are no control box of sig307, so how could I know how many routes it have? I supposed it has 2 routes, one is 307A(S), from 307 to Down Main, another is 307B(S), from 307 to Up Main. And I think 307B(S) is opposing to 114C(M). An I wrong again? I admitted that I could not understand your explanation very well.....

My logic process goes like this:
1. No route table provided; therefore probably only one route (as there is obviously felt there is no need to define).

2. As a cross-check, what destinations could it have?
a) to Down Main: yes it would read to 115
b) to Up Main: no it can't (as there is no exit signal or LOS to which it could read).
Therefore definitely only one route.

Referring to 4b) I did not understand your meaning...could you kindly please explain it again?
"whereas you showed 114C(M) and 114C(C ) correctly, for some reason you got 114D(M) wrong as you claimed that the route would set after the train using the opposing call-on route had timed to a stand. Since the main aspect requires the track clear, the route locking should prevent the route from setting where there is an opposing train even after it has become stationary"

114C(M) and 114C(C ) are correct.
114D(M) should be similar to 114C(M); it therefore confuses me why you got that one wrong.

A Main (or indeed Warning) route should always prove that there is no train facing in the opposite direction, even a stationary opposing move should prevent the route from setting. There is no value in letting the route set, since the aspect requires that track clear then the aspect would stay at danger indefinitely (and signaller could be confused because the route setting suggests that the signal will eventally clear which is untrue).

A Call-on (or indeed permissive shunt) route should prove that there is no train still moving in the opposite direction; however if the that train has occupied a track for long enough that we can be certain that it is at a stand, then the other route can set. Since the aspect does NOT require that track circuit to be unoccupied, it would be able to clear with the train stopped (perhaps in a platform). Therefore it should be obvious that we do need to have permitted the route itself to be set in such a scenario.

Hence the CT for a (M) or (W) route would not [#] have a "or track occupied for time entry", but the CT for a (C ) or (S) route would have such an entry.

Note [#]:
The only time that the CT for a (M) or (W) route would have a "or track occupied for time entry" is when the opposing OVERLAP opposes but the opposing route ITSELF does not oppose. Once the first train has been stopped then its overlap can be reallocated for the opposite direction movement.

Referring to 9
"133A(S) would be "when cleared" as the route is approach released; don't confuse shunt class routes from main signals with shunt signals- there are some subtle differences."
why? I have checked British Railway Control Table, and saw it says "For a subsidiary signal, the approach locking controls and time are the same as for its assocoated main signal". Is it what you mean?

Partly.
A PL that is supplementary to a main signal (probably a R/Y/G or R/Y/YY/G but could actually be any signal having at least a Red) is slightly different from an independent shunt signal (generally a GPL).
A PL supplementary to a main signal could be for a call-on move (permissive passenger) and / or a shunting move; the GPL is only for a shunting move.
Whereas a subsidiary PL would always be approach released, the GPL would not be, since there would be no running move up to it; any train travelling towards it must already be shunting and thus under 15mph.
Comprehensive approach locking for a main running signal can be complex and therefore expensive; hence we only provide if particularly valuable to have facility.
For a GPL we only need one track of minimum distance 50m; therefore always simple and given this then we almost always provide. Therefore GPLs are only "when cleared" if they do not have a suitable berth track circuit.
A PL associated with a main signal will always be approach released; hence by definition there must be a train on the berth track and hence it would be stupid to provide comprehensive approach locking (as we already know that the condition could not be satisfied)!

The quote you have found relates to RRI.
A GPL approach locking timer would normally be 30 seconds; there would be one timer for all routes from the signal. Whereas a subsidiary PL could safely have an approach locking timer of 30s (and to more modern practice with electronic interlockings would be 30sec), it is not economic in relay terms to provide a separate timer just for the (S) routes from the signal; therefore whatever timer is already provided for the main signal (say 120, 180s or 240s) would be utilised for the (S) route. Purely an econmoy measure.

It is truely that I can not get your points sometimes....for Eng is my mother tongue. I will try to communicate with you whenever I have difficulties. And thank you for your detailed explanation again and again......... I usually felt moved when I saw long pages of your detailed explanation. Thanks again.

I know it is difficult. It is often hard to express in terms that are simple enough to understand easily without being possibly misleading.
I think you meant that English is not your mother tongue; I can understand that long amounts of text can be hard. However being too brief and using abbrieviations also may be difficult and therefore more text perhaps helps.
Also you raise some interesting points and my explanation is not just for you but also for others who do have English as their native language, so there must be compromise between different needs of users.
As long as you don't feel too daunted, that is OK