2012 Q8 Interlocking, 2 separate levels

[Hort]

I attempted this question because, at face value, I thought that I could answer it, however, having had a go I have come to the conclusion that if this came up I would probably avoid it! there is too much to write and easy to go off-topic!

[PJW]

I think this was a reasonable attempt.

It didn't however seem that you had too much to write- it was overall a bit on the short side and actually quite an overlap beteen contents of the two halves of the question.

It sounded initally that you were describing Western Region E10k RRI with the split between "non-vital" and "vital", but the I decided that you were not- as you go on to talk about latched relays and push-button rings (which apart from the last panels the WR decided to avoid). I guess however that it probably has its origins in the same 1960s generation - in the days where electonic remote control was either non-exstent or very expensive and none too reliable.

I didn't quite believe the bit about latched relays as the interlocking can't continue to operate without power. perhaps you are refering to NLRs which means that the interloccking can resume promptly once power is restored after a power failure, or perhaps you meant that it was the route relays being fed from the control centre being magnetically latched- this would certainly seem to accird with a first generation electronic TDM whih sometimes suffered intermittant drop outs and by latching the info at the field end would avoid all the signal aspects blipping as a result.

I think it would have been worth your answer mentioning that RRI tends to separate out route and aspect levels even if all achieved by vital relays in the same place- it just so happens that in the system you describe that the opportunity is taken to locate most of the route level at the control centre end.

I also would say that part of the route level has to be at the interlocking end- I don't know the system you desribe but conceptually doesn'tt seem that different to the E10k split. The thing I am certin about ids that the locking of the route via route locking must be undertaken by vital relays within the interlocking (although E10k also does an element of this non-vitally at the anel end as well). Also E10k undertakes the actual calling of the points by the routes at the interlocking end as well- I suspect your system would also do the same.

Hence the route / aspect level split isn't quite the same as the control centre / relay room demarcation.
As you have largely stated, the essence is that-

ROUTE level:
a) undertaken once (at the time the signaller requests route- either it sets "there and then" or request is permanently ignored),
b) checks availability of the individual elements of the route and then the route as an entity,
c) sets up the route by moving the points etc.,
d) imposes the locking and hence establishes the path for the train (or succession thereof)


ASPECT LEVEL:
a) is continually checked to establish that all the conditions are and remain suitable to give the driver a movement authority by clearing the signal,
b) ensures that the locking has been imposed by route setting,
c) ensures the points have actually moved (have detection and the point contactors have dropped out again) etc and therefore proves that the route has actually been established to ensure a locked wheeled path protected by flank and traping as necessary,
d) ensures train separation from previous train (train detection clear, signal at end of movement authority proved alight and backed up by train protection as needed).

I think that you need to keep the 1st part quite high level and go more into the detail in the 2nd part to minimise the duplication between them.

This can go into more specific examples- you could discuss the use of track circuits at route setting level (typically determination of class of rute for permissive passenger etc) as opposed to usage at aspect level:

1. tracks in line of route and overlap,
2. foul to route,
3. flank overrun protection,
4. occupied for approach release,
5. occupied for permissive move,
6. signal disengaging,
7. approach locking release
etc.

Hence I think that your answer had quite a lot of the content needed but perhaps you could have made a bit more of it.

As ever, suggest use of lists, tables etc to give the answer structure, minimise the number of words in long bits of prose. If nothing else it spaces it out so that it looks more and is very "in the face" for the examiner so much harder fo them to miss your pearls of wisdom.

I attempted this question because, at face value, I thought that I could answer it, however, having had a go I have come to the conclusion that if this came up I would probably avoid it! there is too much to write and easy to go off-topic!

[Hort]

thanks, the system that I was primarily describing was E10K, however, I wanted to expand on the description to demonstrate knowledge of BRS RRI as well.

[PJW]

Forum has been very quiet this year, but actually I have had a lot of attempts from a range of individuals, particularly recently; everyone seems very shy in sharing their work......

However I have permission to put some attempts on which I have commented on the Forum, so here is one of them attached with some comments written on and others below.

2012 Q8:

Very full answer.  Clearly you know a lot and can present it well. 

• Looking at your answer I think it met all the functional requirements well; however just don’t believe that you produced all this in 30 mins.  In the exam there is also the non-functional constraint of 30 mins which also has to be observed; if you go over time then you are against the “law of diminishing returns” and throwing away more marks in whatever answer you have stolen the time from, than you’d be gaining extra here. 
  
  
• You must be very rigid on TIME MANAGEMENT and that means WITHIN a question as well as just moving on to the next when time expires.  I appreciate that you may have done this one some time ago when getting as good an answer as possible was the aim; however it is critical that you do get some practice of “doing as good a job as possible over the whole content of a question within time constraint”.  So get some practice doing this; make sure that your internal watchdog time-clock is effective at overriding your natural desire to do as good a job as you can.  In the IRSE Exam, focus is not on perfection but on demonstrating good understanding; just keen that your last minute preparation is focussed on this fine-tuning for exam performance!