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Bite-sized Revision Notes
#1
Several years ago when supporting a small group of Module 3 students remotely, I got into the habit of emailing them a "one-pager" revision note summary almost every working day in much of the last month aproaching the exams.

Various changes of computer system have happened since and I am not absolutely sure that the attachments are the "final" versions of each (there may be some on the Forum who received copies and I'd appreciate knowing if you have "better" ones); however I offer them here.  No particular order- just relatively brief summaries of different topics; not intended as "first-off" learning but as "refreshers".

The first ones are attached here and I'll add more later if there is a demand, so let me know if you find them useful.

regards,
PJW


Attached Files
.docx   IRSE mod3 Bite 03 Shunt.docx (Size: 24.57 KB / Downloads: 25)
.docx   IRSE mod3 Bite 02 Call-on.docx (Size: 22.55 KB / Downloads: 22)
.docx   IRSE mod3 Bite 01 Warner.docx (Size: 22.05 KB / Downloads: 21)
.doc   IRSE mod3 Bite 04 App Rel.doc (Size: 50.5 KB / Downloads: 19)
.docx   IRSE mod3 Bite 19 Level xings.docx (Size: 23.87 KB / Downloads: 20)
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#2
Can you explain the concept of Huddersfield locking? Would be helpful if you can post some notes explaining this.

Thank you.

PJW Wrote:Several years ago when supporting a small group of Module 3 students remotely, I got into the habit of emailing them a "one-pager" revision note summary almost every working day in much of the last month aproaching the exams.

Various changes of computer system have happened since and I am not absolutely sure that the attachments are the "final" versions of each (there may be some on the Forum who received copies and I'd appreciate knowing if you have "better" ones); however I offer them here. No particular order- just relatively brief summaries of different topics; not intended as "first-off" learning but as "refreshers".

The first ones are attached here and I'll add more later if there is a demand, so let me know if you find them useful.

regards,
PJW
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#3
Please ignore my earlier posting concerning Huddersfield locking. Found the answer on page 47 Section 7.3.6 of the Control Tables and Principles Notes.

Thank you


alexgoei Wrote:Can you explain the concept of Huddersfield locking? Would be helpful if you can post some notes explaining this.

Thank you.

PJW Wrote:Several years ago when supporting a small group of Module 3 students remotely, I got into the habit of emailing them a "one-pager" revision note summary almost every working day in much of the last month aproaching the exams.

Various changes of computer system have happened since and I am not absolutely sure that the attachments are the "final" versions of each (there may be some on the Forum who received copies and I'd appreciate knowing if you have "better" ones); however I offer them here. No particular order- just relatively brief summaries of different topics; not intended as "first-off" learning but as "refreshers".

The first ones are attached here and I'll add more later if there is a demand, so let me know if you find them useful.

regards,
PJW
Reply
#4
PJW Wrote:The first ones are attached here and I'll add more later if there is a demand, so let me know if you find them useful.

regards,
PJW

After the Signet weekend I have been asked verbally to load more here; I really can't understand why members seem so reluctant to post anything publically but prefer to deal privately even for such requests.....


Attached Files
.docx   IRSE mod3 Bite 07 Approach locking.docx (Size: 24.89 KB / Downloads: 21)
.jpg   IRSE mod3 Bite 06b opposing route locking coloured sketch.JPG (Size: 311.13 KB / Downloads: 27)
.docx   IRSE mod3 Bite 06a Opposing Route locking.docx (Size: 23.82 KB / Downloads: 24)
.docx   IRSE mod3 Bite 05 Aspect seq charts.docx (Size: 22.3 KB / Downloads: 18)
.docx   IRSE mod3 Bite 08 Junction Signalling 2006.docx (Size: 27.05 KB / Downloads: 18)
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#5
More bites


Attached Files
.docx   IRSE mod3 Bite 12 Flashing aspects.docx (Size: 22.07 KB / Downloads: 21)
.doc   IRSE mod3 Bite 11 Preset shunts.doc (Size: 251 KB / Downloads: 20)
.doc   IRSE mod3 Bite 10 Platform sharing.doc (Size: 363.5 KB / Downloads: 20)
.docx   IRSE mod3 Bite 09 Replacement.docx (Size: 23.9 KB / Downloads: 22)
.docx   IRSE mod3 Bite 14 TPWS.docx (Size: 676.85 KB / Downloads: 20)
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#6
That's the lot!

Now read, mark, learn and inwardly digest........

PJW


Attached Files
.docx   IRSE mod3 Bite 17 Non technical prep.docx (Size: 22.45 KB / Downloads: 21)
.pdf   IRSE mod3 Bite 16b pictures.PDF (Size: 307.23 KB / Downloads: 23)
.docx   IRSE mod3 Bite 16a Single line block minus pics.docx (Size: 25.55 KB / Downloads: 19)
.docx   IRSE mod3 Bite 15 Double line block.docx (Size: 456.91 KB / Downloads: 18)
.docx   IRSE mod3 Bite 18b Point locking checklist.docx (Size: 15.62 KB / Downloads: 20)
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#7
PJW Wrote:That's the lot!

Now read, mark, learn and inwardly digest........

PJW

PJW Wrote:That's the lot!

Now read, mark, learn and inwardly digest........

PJW

Dear PJW,

It is really useful, but I have several queries on the Notes:

1. Bite 6 Opposing Route locking (Point 8 & 9)
- I am not too used to using the bracket for the time released statement, can you explain more about the meaning of the bracket?
- For Point 9, why the T.C. to be enclosed withing a bracket is different for non-permissive opp. route & permissive opp. route?
- Can I omit the use of bracket like the old style C.T. samples?

2. Bite 6 Opposing route locking (Point 10)
- If there is really an opp. route infringing one side of the swinging O/L only, do I just igore it? or I just write it without a point condition (of the swinging O/L point?)

3. Bite 18 Points (Point 3 bullet 5)
- For a point lying in a swinging overlap (but not the swinging O/L point), I think the route locking requires a condition on the position of the swing O/L point. Is there other ways to express this if we do not add a point condition?

4. Bite 18 Points (Point 6 bullet 3)
- Can you explain more why the route lock only needs to maintain after berth TC clear, but not require us to write all T.C from start signal till the berth TC?

Actually for the Point Control Table, I plan to use an old style C.T. (I think back to British Railway times...) that have blanks provided for Swinging O/L, and unlike NR practice it will not separate 2 rows for N->R & R->N cases (N->R and R->N will only be mentioned only when required). In the examples that I have it does incorporate point conditions when the points concern swinging overlap cases. Do you think it is acceptable for the examiner?
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#8
I have been away, so a backlog of things to do!

I'll try to get around to your queries as soon as I can, but in the meantime, have you looked at:
http://www.irseexam.co.uk/attachment.php?aid=29

I think this should provide some answers; however basically brackets are "to hold expressions together".  There are two main reasons where they are used;

1) to avoid "ambiguity" where there is an expression of the form: A, B or C.
Colloquially this means A or B or C but mathmatically it doesn't!
It actually means "either both A AND B must be true or alternatively C must be true" for expression to be satisfied.
If you want it to mean "A must be true AND also either of B or C must be true", then you need brackets- viz: A, (B or C)

2) Where a single expression spans adjacent columns in a Control Table.  To be honest when two column are cleary related, such as track occupied and the "for time", then they can be omitted but it is always safer to put in.  An alternative presentation links the entries in the two columns by dashes- this was perhaps more common when CT's handdrawn than when CAD is used.  Indeed if we need to link entries in multiple columns or non-adjacent columns then we often use both the brackets and the dashes.


Attached Files
.docx   IRSE mod3 Bite 18b Point locking checklist.docx (Size: 15.62 KB / Downloads: 8)
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#9
YLP Wrote:[I have several queries on the Notes:

1. Bite 6 Opposing Route locking (Point 8 & 9)
- I am not too used to using the bracket for the time released statement, can you explain more about the meaning of the bracket?
- For Point 9, why the T.C. to be enclosed withing a bracket is different for non-permissive opp. route & permissive opp. route?
- Can I omit the use of bracket like the old style C.T. samples?

The opening position of the bracket is significant in determining the extent of the opposing route locking that is bypassed when the train has come to a stand. Generally the train needs to be timed on the last track, but if there is a rational reason- such as a platform- for a train to come to a stand prior to the last track then the timing may be on two or more combined. For obvious reaons any of the tracks on which the timing is performed must be "within the brackets" in the route locking column, but potentially there may be more than that. SSI generally only bypasses the bare minimum whereas RRI generally bypasses ALL the tracks back to the opposing signal; i.e. a track occupied for time overrides all the route locking (but NOT the actual Route Normal).

One can argue that SSI is therefore slightly "safer" in this regard; even if there is a rightside track failure on the timimng track, the route locking prior to this is still tested to be free, whereas in RRI it is not- however I think the real reason for the difference is that SSI relies upon the sub-routes to carry the approach locking of the opposing entrance signal whereas RRI does include this explicitly (to cover timing issues) despite it being in the route locking cascade relays as well. Hence actually what a Control Table shows is dependent on technology; I generally default to showing SSI as it is the default technology on NR BUT EACH CANDIDATE CAN FOLLOW THEIR KNOWN PRACTICES.

In SSI therefore the brackets are 100% essential. Less so on RRI since the unwritten convention is that the timing tracks always bypass all the route locking in the preceding column; however I'd still show as it is more explicit and can certainly give clarity where entry spans a couple of lines of text etc.

Re your second query.
If a train has come to a stand it will have timed out its overlap but the route locking under the train will still be locked. This should prevent an opposing Main or Warning route being set (being non-permissive the aspect won't be able to clear hence to allow the route to set would be a waste and also mislead the signaller). However a Call-on or Shunt (assuming permissive) should be allowed to set despite the locked sub-route (i.e. bypasssed by the track timer) since the aspect will be able to clear to allow a second train / loco to attach to the previous train.
However in most cases we wouldn't want to simultaneously allow another train to be routed on to the first train from the opposite direction. Sometimes historically we did allow this (era of parcels traffic, loco changes, adding and taking off vehicles at main stations when an express stopped)- referred to as "topping and tailing". Only provided where necessary for traffic; there is always the risk that the track occupancy may not be a train at all but a track failure and having trains routed head-on albeit only on PL aspects is still not good!
Therefore the significance of the bracket position- does the track occupancy bypass just the locking for that track, or for all the tracks prior to it as well; this determines whether can "top'n'tail".
Also remember the mere fact that a Call-on has been able to be set suggests that the track timer on the berth exit track will already be occupied before the second train even enters the route; indeed it is very likely to have reached the time out value well before the second train gets anywhere near it (because the first one has been sitting there!). Hence if you bridge out all the route locking sections due to the timer having completed, nothing would stop the setting of a permissive route from the other direction; there is no risk of that happening with a non-permissive route as the exit track route locking is not itself bypassed by the track timer, so the simpler logic suffices.

Do note the use of passenger permissive platforms, especially for platform sharing by different trains, is looked upon less favourably nowadays; see GK/RT0044 for the relevant additional locking.
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#10
YLP Wrote:2. Bite 6 Opposing route locking (Point 10)
- If there is really an opp. route infringing one side of the swinging O/L only, do I just ignore it? or I just write it without a point condition (of the swinging O/L point?)

Some people when writing the string of tracks that impose locking after a route used start writing point conditions within that list, almost as if it were the tracks in aspect for a swinging overlap; this is wrong!

Generally if there is a swinging overlap within the "opposing route" for the one for which you are writing the CT, then one lie of the points opposes your route and one does not. You should list all the tracks for the route and the lie of the points that oppose but then condition out THE WHOLE LOT (including the Route Normal) by the availability of the set of hinge points to swing away and thus no longer oppose the CT route. Having written (I think in 2005) that to get such an example in IRSE Exam would be unusual, just look at the 2006 layout and the recent comments I gave Alex where there was not just the one example, but several! Just goes to show that you may have to cope with anything......
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