https://irse.signalpost.org/ Wed, 22 Apr 2026 13:41:35 +0000 MyBB https://irse.signalpost.org/showthread.php?tid=1439 Wed, 24 Jul 2013 14:02:24 +0000 adobe]]> https://irse.signalpost.org/showthread.php?tid=1439 Many thanks in advance
Ad]]> Many thanks in advance
Ad]]> https://irse.signalpost.org/showthread.php?tid=1418 Wed, 19 Jun 2013 05:56:35 +0000 PJW]]> https://irse.signalpost.org/showthread.php?tid=1418
I have some problems regarding control table. Actually some times I confused direct and indirect interlocking- a route which according to me should be direct was actually indirect, so please help me & explain it with some examples.

First let's go over some basics for background knowledge before trying to answer the actual question asked.


Firstly you must get the concept (which probably differs from the usual case in India and is certainly different from the traditional London Underground approach) of SECTIONAL route release.
When a route is set from entrance signal to exit signal, then all points anywhere along the route itself, its flank and its overlap are initially locked; HOWEVER once the entrance signal has returned to red after the passage of the train and is free of approach locking, then it is only those points which have not yet been traversed which remain locked- the points are "freed-up" behind the train. Locking is held "in front" of the train; points are free "behind" the train; points which were locked initially no longer are. It is when these points were the only thing preventing the setting of the conflicting route that INDIRECT route locking becomes necessary.

Note therefore when considering the locking between 2 routes, the situation is not always symmetrical.
Hence it is important to think about separately:
1. A train passing through "route a" at the time that "route b" is requested,
2. A train passing through "route b" at the time that "route a" is requested,

When doing a Control Table for "route a" you need to think of the signaller attempting to set that one as a new route in the scenario of the historical situation of a train having previously been signalled via "route b" and ask the 2 separate (but related) questions-

i) Is "route b" still locking points in a lie which is incorrect for "route a"? if so the routes are incompatible but it is the point locking which is preventing. The point availability checks for "route a" will not be satisfied and thus route setting is prevented. Route locking is not shown (even if within the circuits / data it is actually included by default),

ii) Should "route b" prevent the setting of "route a"? If it should (because the train on "route b" is still coming towards the train for which we want to set "route a") then we need to show "opposing route locking" on the Control Table, unless the locking is "via the points" as in i) above.

Now to come to the question asked.
DIRECT locking is the situation when the 2 routes mutually lock each other- the point locking imposed by "route a" and that imposed by "route b" is identical within the length of railway which they share. A train using "route a" opposes "route b" until that train gets behind "signal a"; similarly a train using "route b" opposes "route a" until that train gets behind "signal b". This is the symmetrical situation; it should be obvious that there needs to be locking since the point availability test for one would be satisfied in the situation that the other route IS CURRENTLY set; in the absence of different point locking the Control Tables must show the opposing route locking in order to prevent trains being signaled head-on to each other.

INDIRECT locking is the situation when there is some difference in the point requirements between "route a" and "route b" within the length of railway which they share. Hence it may seem that there is no need for opposing locking; at first sight the locking seems to be being provided by virtue of the different point locking; HOWEVER as the first train progresses through its route, then that incompatibility of point locking will subsequently disappear (since the points which were initially locked in an incompatible lie later become free). Therefore there is a need to provide opposing locking in order to prevent the other route setting when this would be undesirable. Note the lack of symmetry in such a scenario; of "route a" CT requires INDIRECT route locking after "route b" then "route b" CT will not feature any reference to "route a" (because the locking of the points the "wrong way"). It is locking that has to be shown because the route WAS PREVIOUSLY SET but wouldn't be needed WHILST opposing route STILL SET but is only necessary after it has been cancelled. Obviously it has to be shown on the Control Tables just like for direct locking but the rationale is for the scenario once the associated point locking has been released by the opposing train being in "mid-route".

The attachment shows a simple layout and tries to show which routes are shown as apposing routes on the Control Tables for just two of the routes- 3A and 8B.
The directly opposing in 3A's CT is 8B. Conversely the directly opposing in 8B's CT is 3A. Symmetry.
To find the all the indirectly opposing routes, look at all the "parallel" signals of the one listed as being directly opposing- once the routes have converged a train on a track circuit could actually have originally come from any of the parallel signals.

Having read this and when you think you have understood it, then look at other posts in this section that relate to opposing route locking, for example this one

PJW]]>
I have some problems regarding control table. Actually some times I confused direct and indirect interlocking- a route which according to me should be direct was actually indirect, so please help me & explain it with some examples.

First let's go over some basics for background knowledge before trying to answer the actual question asked.


Firstly you must get the concept (which probably differs from the usual case in India and is certainly different from the traditional London Underground approach) of SECTIONAL route release.
When a route is set from entrance signal to exit signal, then all points anywhere along the route itself, its flank and its overlap are initially locked; HOWEVER once the entrance signal has returned to red after the passage of the train and is free of approach locking, then it is only those points which have not yet been traversed which remain locked- the points are "freed-up" behind the train. Locking is held "in front" of the train; points are free "behind" the train; points which were locked initially no longer are. It is when these points were the only thing preventing the setting of the conflicting route that INDIRECT route locking becomes necessary.

Note therefore when considering the locking between 2 routes, the situation is not always symmetrical.
Hence it is important to think about separately:
1. A train passing through "route a" at the time that "route b" is requested,
2. A train passing through "route b" at the time that "route a" is requested,

When doing a Control Table for "route a" you need to think of the signaller attempting to set that one as a new route in the scenario of the historical situation of a train having previously been signalled via "route b" and ask the 2 separate (but related) questions-

i) Is "route b" still locking points in a lie which is incorrect for "route a"? if so the routes are incompatible but it is the point locking which is preventing. The point availability checks for "route a" will not be satisfied and thus route setting is prevented. Route locking is not shown (even if within the circuits / data it is actually included by default),

ii) Should "route b" prevent the setting of "route a"? If it should (because the train on "route b" is still coming towards the train for which we want to set "route a") then we need to show "opposing route locking" on the Control Table, unless the locking is "via the points" as in i) above.

Now to come to the question asked.
DIRECT locking is the situation when the 2 routes mutually lock each other- the point locking imposed by "route a" and that imposed by "route b" is identical within the length of railway which they share. A train using "route a" opposes "route b" until that train gets behind "signal a"; similarly a train using "route b" opposes "route a" until that train gets behind "signal b". This is the symmetrical situation; it should be obvious that there needs to be locking since the point availability test for one would be satisfied in the situation that the other route IS CURRENTLY set; in the absence of different point locking the Control Tables must show the opposing route locking in order to prevent trains being signaled head-on to each other.

INDIRECT locking is the situation when there is some difference in the point requirements between "route a" and "route b" within the length of railway which they share. Hence it may seem that there is no need for opposing locking; at first sight the locking seems to be being provided by virtue of the different point locking; HOWEVER as the first train progresses through its route, then that incompatibility of point locking will subsequently disappear (since the points which were initially locked in an incompatible lie later become free). Therefore there is a need to provide opposing locking in order to prevent the other route setting when this would be undesirable. Note the lack of symmetry in such a scenario; of "route a" CT requires INDIRECT route locking after "route b" then "route b" CT will not feature any reference to "route a" (because the locking of the points the "wrong way"). It is locking that has to be shown because the route WAS PREVIOUSLY SET but wouldn't be needed WHILST opposing route STILL SET but is only necessary after it has been cancelled. Obviously it has to be shown on the Control Tables just like for direct locking but the rationale is for the scenario once the associated point locking has been released by the opposing train being in "mid-route".

The attachment shows a simple layout and tries to show which routes are shown as apposing routes on the Control Tables for just two of the routes- 3A and 8B.
The directly opposing in 3A's CT is 8B. Conversely the directly opposing in 8B's CT is 3A. Symmetry.
To find the all the indirectly opposing routes, look at all the "parallel" signals of the one listed as being directly opposing- once the routes have converged a train on a track circuit could actually have originally come from any of the parallel signals.

Having read this and when you think you have understood it, then look at other posts in this section that relate to opposing route locking, for example this one

PJW]]> https://irse.signalpost.org/showthread.php?tid=1043 Mon, 25 Jun 2012 20:17:33 +0000 wealdbrook]]> https://irse.signalpost.org/showthread.php?tid=1043
the briefing CD sent out to candidates has an error on it, an errata will be issued.

The format for Module 3 will be (as last year) a selection of questions all with equal marks.

One question will be to prepare some control tables using either the supplied blanks or blanks brought in by candidates (subject to their being no corporate identifiers).

There will be a selection of written questions covering mainline and metro railways with opportunities for all backgrounds to find a selection they should be able to answer.

There may be an aspect sequence chart question and if so this will cater for practices other than UK practice.

All candidates are encouraged to attempt past papers and have their answers reviewed in study groups, by senior members in their organisation or their peers.

Candidates are reminded to read the question carefully, to observe the distribution of marks and answer the question set.

The Exam Committee wish all candidates all the best in all modules.]]>
the briefing CD sent out to candidates has an error on it, an errata will be issued.

The format for Module 3 will be (as last year) a selection of questions all with equal marks.

One question will be to prepare some control tables using either the supplied blanks or blanks brought in by candidates (subject to their being no corporate identifiers).

There will be a selection of written questions covering mainline and metro railways with opportunities for all backgrounds to find a selection they should be able to answer.

There may be an aspect sequence chart question and if so this will cater for practices other than UK practice.

All candidates are encouraged to attempt past papers and have their answers reviewed in study groups, by senior members in their organisation or their peers.

Candidates are reminded to read the question carefully, to observe the distribution of marks and answer the question set.

The Exam Committee wish all candidates all the best in all modules.]]> https://irse.signalpost.org/showthread.php?tid=969 Mon, 04 Jul 2011 16:42:04 +0000 Peter]]> https://irse.signalpost.org/showthread.php?tid=969
]]>
]]> https://irse.signalpost.org/showthread.php?tid=737 Sat, 05 Feb 2011 21:41:34 +0000 PJW]]> https://irse.signalpost.org/showthread.php?tid=737
Firm details will no doubt be made available formally in due course, but the attachment is the version that was distributed at the event and thus the best information currently available.

See also the information in the Exam Review thread re the likely changes in the Module 3 paper for this year.


]]>
Firm details will no doubt be made available formally in due course, but the attachment is the version that was distributed at the event and thus the best information currently available.

See also the information in the Exam Review thread re the likely changes in the Module 3 paper for this year.


]]> https://irse.signalpost.org/showthread.php?tid=691 Mon, 08 Nov 2010 21:30:11 +0000 sgm1983]]> https://irse.signalpost.org/showthread.php?tid=691 https://irse.signalpost.org/showthread.php?tid=514 Sun, 25 Jul 2010 08:13:48 +0000 merlin89]]> https://irse.signalpost.org/showthread.php?tid=514 Thanks
Ian]]> Thanks
Ian]]> https://irse.signalpost.org/showthread.php?tid=368 Sat, 03 Apr 2010 07:07:01 +0000 PJW]]> https://irse.signalpost.org/showthread.php?tid=368 It certainly seems from the 2004 CTs that more clarity on Comprehensive A/L is needed. I haven't finished it, but in case anyone is wanting to use the Easter period to have a go at some more Control Tables (for example the 2009 i/c/w the Signet event in just over a month's time), I thought it best to post the part which I have now written even though it is incomplete.

Now added a bit more]]> It certainly seems from the 2004 CTs that more clarity on Comprehensive A/L is needed. I haven't finished it, but in case anyone is wanting to use the Easter period to have a go at some more Control Tables (for example the 2009 i/c/w the Signet event in just over a month's time), I thought it best to post the part which I have now written even though it is incomplete.

Now added a bit more]]> https://irse.signalpost.org/showthread.php?tid=342 Fri, 05 Mar 2010 17:48:01 +0000 interesting_signal]]> https://irse.signalpost.org/showthread.php?tid=342
Looking at the diagram on page 44 of "Control Tables PJW.doc" (section 7.3.4), if a train is travelling from signal 22 to 18 and only occupying SF track having cleared SG, 931 points will be free to move reverse, and so the route from 24 to 18 could be set (although it wouldn't get the aspect because of the train on SF). In the route control tables for 22 signal, would 24 be an opposing route?

Any comments or hints would be appreciated.]]>
Looking at the diagram on page 44 of "Control Tables PJW.doc" (section 7.3.4), if a train is travelling from signal 22 to 18 and only occupying SF track having cleared SG, 931 points will be free to move reverse, and so the route from 24 to 18 could be set (although it wouldn't get the aspect because of the train on SF). In the route control tables for 22 signal, would 24 be an opposing route?

Any comments or hints would be appreciated.]]> https://irse.signalpost.org/showthread.php?tid=331 Wed, 10 Feb 2010 14:34:42 +0000 merlin89]]> https://irse.signalpost.org/showthread.php?tid=331 https://irse.signalpost.org/showthread.php?tid=327 Fri, 05 Feb 2010 16:46:43 +0000 merlin89]]> https://irse.signalpost.org/showthread.php?tid=327
Where to start if you know nothing about trains how about at the beginning.
1. ABC Modern Signalling Handbook by Stanley Hall
2. Two Centuries of Railway Signalling by Alan Williams and Geoffrey Kichenside
3. The First Principles of Railway Signalling By C. B. Byles
4. British Railway Signalling by Geoffrey Kichenside

Books From IRSE

1. Introduction to Railway Signalling
2. Railway signalling by OS Nock
3. Railway Control Systems by Maurice Leach]]>
Where to start if you know nothing about trains how about at the beginning.
1. ABC Modern Signalling Handbook by Stanley Hall
2. Two Centuries of Railway Signalling by Alan Williams and Geoffrey Kichenside
3. The First Principles of Railway Signalling By C. B. Byles
4. British Railway Signalling by Geoffrey Kichenside

Books From IRSE

1. Introduction to Railway Signalling
2. Railway signalling by OS Nock
3. Railway Control Systems by Maurice Leach]]> https://irse.signalpost.org/showthread.php?tid=310 Sun, 13 Dec 2009 10:33:24 +0000 merlin89]]> https://irse.signalpost.org/showthread.php?tid=310 Thanks in advance]]> Thanks in advance]]> https://irse.signalpost.org/showthread.php?tid=306 Sat, 21 Nov 2009 10:30:35 +0000 merlin89]]> https://irse.signalpost.org/showthread.php?tid=306 https://irse.signalpost.org/showthread.php?tid=268 Wed, 19 Aug 2009 20:37:13 +0000 PJW]]> https://irse.signalpost.org/showthread.php?tid=268 https://irse.signalpost.org/showthread.php?tid=247 Thu, 25 Jun 2009 17:30:58 +0000 PJW]]> https://irse.signalpost.org/showthread.php?tid=247 Quote:xxxxxxxxx from IRSE Exam has sent you the following message:
------------------------------------------
Hi,
Network Rail Standard NR/L3/SIG/11202 depicts a new format of Control Table where as one of the Post in this Site is of an older one.
Please clarify the exact format that can be used if I want to attempt control tables with UK railway signalling principles.

Thanks & Regards.
------------------------------------------
It is quite clear; you can use ANY format with which you are familiar- this does not have to be exactly like any particular format of any particular railway. You'd be well advised to base it on one with which you are familiar, but do not be afraid to simplify it a bit- what is a good format for CAD / automated production in a real environment probably isn't for exam conditions.

The new standard (which incidentally I played a significant part in producing) will hardly yet have been used anywhere- I doubt whether any site has been commissioned that uses it yet. Hence I feel it unlikely that it would be anyone's preferred format. Indeed it has been designed exclusively for SSI (and derivatives) and has benefits for complicated areas and gives overall economy by separating out the route locking and approach locking lookback etc and putting on separate tables and utilises summation Control Tables. The overhead of producing these for the whole layout when only being asked to do the Control Tables for a couple of points and a few routes renders it TOTALLY INAPPROPRIATE for the exam. I guarantee that the examiners won't know the details of the new standard and may even be unaware of its existence- most of the regular mod3 examiners don't actually work for Network Rail!

I wouldn't use the previous version of 11202 either- at least without considerable simplification as explained in previous posts and for which several student's modified versions appear as examples on this site.

If you read the various past exam reviews you'll discover that the examiners generally recommend use of a column based Control Table. I think they may well be right re speed in the exam is concerned, and again there are examples of such on this site. If you are starting from scratch then I'd recommend; if however you work entails regular use of the older 11202 and you are experienced with them, then perhaps worth using a design based on that style to avoid needing to re-learn and potentially confusing yourself.

See also:
http://www.irseexam.co.uk/showthread.php...ght=format

http://www.irseexam.co.uk/showthread.php...ight=11202]]> Quote:xxxxxxxxx from IRSE Exam has sent you the following message:
------------------------------------------
Hi,
Network Rail Standard NR/L3/SIG/11202 depicts a new format of Control Table where as one of the Post in this Site is of an older one.
Please clarify the exact format that can be used if I want to attempt control tables with UK railway signalling principles.

Thanks & Regards.
------------------------------------------
It is quite clear; you can use ANY format with which you are familiar- this does not have to be exactly like any particular format of any particular railway. You'd be well advised to base it on one with which you are familiar, but do not be afraid to simplify it a bit- what is a good format for CAD / automated production in a real environment probably isn't for exam conditions.

The new standard (which incidentally I played a significant part in producing) will hardly yet have been used anywhere- I doubt whether any site has been commissioned that uses it yet. Hence I feel it unlikely that it would be anyone's preferred format. Indeed it has been designed exclusively for SSI (and derivatives) and has benefits for complicated areas and gives overall economy by separating out the route locking and approach locking lookback etc and putting on separate tables and utilises summation Control Tables. The overhead of producing these for the whole layout when only being asked to do the Control Tables for a couple of points and a few routes renders it TOTALLY INAPPROPRIATE for the exam. I guarantee that the examiners won't know the details of the new standard and may even be unaware of its existence- most of the regular mod3 examiners don't actually work for Network Rail!

I wouldn't use the previous version of 11202 either- at least without considerable simplification as explained in previous posts and for which several student's modified versions appear as examples on this site.

If you read the various past exam reviews you'll discover that the examiners generally recommend use of a column based Control Table. I think they may well be right re speed in the exam is concerned, and again there are examples of such on this site. If you are starting from scratch then I'd recommend; if however you work entails regular use of the older 11202 and you are experienced with them, then perhaps worth using a design based on that style to avoid needing to re-learn and potentially confusing yourself.

See also:
http://www.irseexam.co.uk/showthread.php...ght=format

http://www.irseexam.co.uk/showthread.php...ight=11202]]>