Yeovil Town signalling question

[Rick-H]

Hi all.

I have been a lurker for quite some time, trying to absorb all the information I can. The only experience I have with railways is modelling, so I had a lot to learn.

 

As I had / given locomotives from GWR/WR, SR and MR, my railway is based upon the Yeovil area where the Great Western Railway and Southern Railway shared Yeovil Town station and had visitors from other railways.

 

The time scale is from early 1950's to mid 1960's i.e. the end of era 4 (BR early crest) to the end of era 5 (BR late crest).

 

In my world I have assumed BR doubled the track between Yeovil Town and Langport Junction and upgraded it to RED availability. They then gave Southern Region running rights over the route. This gave WR a diversionary route and SR a more direct route to North Devon. Then in the 1960’s Mr. Beaching did not close the Yeovil Town to Taunton line, so Yeovil Town station and its shed were not closed.

 

My model is of Yeovil Town, with a lot of licence. It is a double track circle with an 10 track fiddle yard off scene.

 

Below is a list of movements, which defined the signalling layout for the station.

 

Passenger Train movements

Up Pull/Push to Platform 1

Platform 1 Pull/Push to Down

Up to Platform 2

Platform 2 to Up

Platform 2 to Branch

Branch to Platform 2

Platform 2 to Down

Down to Platform 3

Platform 3 to Down

Goods Train Movements

Up to Goods Sidings

Up Goods Through

Up Goods to Branch

Down to Goods Sidings

Goods Sidings to Up

Goods Sidings to Down

Light Engine movements

Platform 2 East end to Shed

Platform 2 West end to Shed

Platform 3 West end to Shed

Shed to Platform 2 – East end, for Up

Shed to Platform 2 – West end, for Down

Shed to Platform 3 for Down

 

I have chosen to signal using Colour Lights, as being a pensioner and on limited funds I can scratch build working CL signals.

 

I am sorry for the long story, however I would appreciate it if someone would look at my signalling and comment on it good or bad and advise any changes I should make.

 

Thanks for your help

Rick

[The Stationmaster]

I do like the basic idea - a good 'might have been' and the track layout at the station is very good and typical of the latter part of that period if signalled with colour lights.

 

Main thing I would say is that some of the running signals should be 3 aspect - 2a, 12, 20, & 26.    2b is presumably a yellow light GPL - as it should be.  Ideally I would,  for that period, expect to see it signalled to WR standards so some of the position light subs on the running signals would not have been provided - 12 & 24.  L1 would/could be GF worked but all the other loco shed points would be handpoints.  

 

 

[5BarVT]

I always liked Yeovil Town as an interesting layout.  Interesting in that there was a signalled route from Taunton to Yeovil Jn but not the other way.

If I were doing this model (and I’m not!) I would still want the opportunity to run a Junction - Town and back service so I would make 25 a main signal.

Paul.

[Rick-H]

Mike,

Thank you for your comments. I hope you don’t mind, but they generate a number of questions in my mind.

You say “running signals should be 3 aspect - 2a, 12, 20, & 26”.

Did you mean signal 1 not 2a, which is an APL?

Also, why only 1, 12, 20 & 26 and not 9, 10, 17 & 23?

If I remove APLs 13 (you said 12) and 24, why not 2a & 11?

In addition if the APLs are removed how would the Light Engine movements be signalled?

 

Re your comments on the Loco Shed Ground Frame, I understand your point, however please allow me modelling licence, as the signal box is in fact my layout control panel.

 

Rick

[Rick-H]

Paul,

Thank you for your comments.

Your point about making signal 25 a main signal is well made, especially as I have M7 class loco number 30129 complete with BR/SR Pull-Push Coach Set 608, just for the Town / Junction shuttle.

 

Rick

[5BarVT]

4 hours ago, Rick-H said:

You say “running signals should be 3 aspect - 2a, 12, 20, & 26”.

Did you mean signal 1 not 2a, which is an APL?

I nearly commented on that, so I’m going to interfere anyway!!

He does mean 1.

4 hours ago, Rick-H said:

Also, why only 1, 12, 20 & 26 and not 9, 10, 17 & 23?

1, 12, 20 & 26 read up to signals on the same box so need something to give a yellow approaching the red.  9, 10, 17 and 23 can be assumed to read out into the section so there will be a distant signal somewhere out there first.

 

4 hours ago, Rick-H said:

If I remove APLs 13 (you said 12) and 24, why not 2a & 11?

2a is needed to signal into the sidings, 11 is needed to signal up to the limit of shunt neither of those moves can use a main aspect.

 

Now, in respect of the Limit of Shunt - you have used a modern symbol, that style of shunt signal with 2 red lamps didn’t come in until well after your time period.  Being WR, you would have an internally illuminated sign saying “Limit of Shunt” in red.

 

4 hours ago, Rick-H said:

In addition if the APLs are removed how would the Light Engine movements be signalled?

A question my former operating colleagues brought up on LMS/ScR practice asked.  They would always provide such a shunt signal until national principles said not to.  Then they wanted to know how the driver would know to stop behind the set back signal and not shoot off down the line.  Some regions (WR) expected the driver to know what he was doing!

So the answer to your question is that you clear the main aspect up to the next signal but the driver knows where to stop in order to set back.

(They are doing exactly that today at Hooton on the Ellesmere Port branch because of heat issues towards Chester.)

 

5 hours ago, Rick-H said:

Re your comments on the Loco Shed Ground Frame, I understand your point, however please allow me modelling licence, as the signal box is in fact my layout control panel.

One way to require slightly less modellers licence would be to label it “Loco Yard Hand Points”

 

All very good questions.

Paul.

[5BarVT]

Some more signal engineers pedanticism for you to consider (and “can’t be bothered” is a perfectly acceptable answer!).

 

Point Numbering: at the time you are considering the A (or a) end would be nearer the box so 4, 6 and 15 would have a and b ends swapped.

The loco shed trap would be numbered with 22 so 22 becomes 22a and the trap becomes 22b.

 

Are you assuming (pretend) mechanically worked points (your dummy FPL switches make me think you are)?

 

Having saved two ‘levers’/switches from 13 and 24 you need to use one of them to separate 2a and 2b so that the signalman can control which one clears (otherwise, he potentially could have two trains signalled towards each other over the crossover).

Ideally you would find an extra one so that both routes off 1 and both routes off 17 can be controlled independently.  (Depends whether you want to imitate a box or just control the trains.)  There are boxes that would use a single switch for both routes these days but I don’t think WR or SR would back then.  (LMS did, and other funny stuff to save a lever here and there.)

You haven’t got a route from 20 to the Down Platform (and your operating requirements don’t call for one).  If you might want to add at some stage in the future it would be better to have a design that includes and cut back initially than one that makes it very difficult to add.

 

Finally if you are trying to imitate a real box, the signals and points wouldn’t be quite numbered in your sequence.  If you would like more realistic numbering just ask and I’ll come up with something.

 

Paul.

[The Stationmaster]

Sorry - yes I did mean 1. (the signal would actually only have one number but I can see a. why you have used two so no worries). 

 

Paul appears to have already answered all the other of your queries regarding my comments and I agree with all his responses so I won't repeat them.

 

Limit of Shunt (LoS) signals using two reds didn't come in until the early 1990s and on thh WR a campaign changeover  from LoS illuminated signs to the new signals commenced c.1992/93

[Rick-H]

Paul,

Your 2 replies are great, thanks.

 

My plan is to implement them all from the first post, however just a few questions / responses to your second one.

 

My “pretend” is electrically operated mechanical points with Track Circuits. That way I do not have to run point rods on the model. I will fit dummy Point Motors (mine are solenoid operated below board) and Facing Point Locks, so the FTP levers are just for show.

 

I understand about 2a & 2b, however I did it that way, because in my software (using a PIC to interlock signals with correct point movements) 2a only cleared if signal 2 was pulled and point 4 is reversed. Point 2b only cleared if signal 2 was not pulled and point 4 is reversed. I now know better, thanks will change.

 

“You haven’t got a route from 20 to the Down Platform”, my logic was that I read somewhere that platforms 1 & 2 were WR and platform 3 was SR. Also I have a route from Branch (20) to platform 2 (10) via West Crossover to Down, which I though achieved the same thing.

 

It is very good of you to offer to correctly renumber the signal box and I would like to take you up on the offer. Would it be easer for you if I make the changes above and give you a revised drawing?

 

Again thanks for all your help

Rick

[Rick-H]

Mike,

 

Thanks.

[5BarVT]

2 hours ago, Rick-H said:

“You haven’t got a route from 20 to the Down Platform”, my logic was that I read somewhere that platforms 1 & 2 were WR and platform 3 was SR. Also I have a route from Branch (20) to platform 2 (10) via West Crossover to Down, which I though achieved the same thing.

It does, sort of!

https://www.s-r-s.org.uk/html/gwe/S3433.htm

This should take you to a thumbnail of Yeovil Town and while you can’t see the signal numbers you can see the track layout.  WR was only a single line but with two platform faces SR had two further platform faces which I guess were numbered 3 and 4.

 

2 hours ago, Rick-H said:

My “pretend” is electrically operated mechanical points with Track Circuits. That way I do not have to run point rods on the model. I will fit dummy Point Motors (mine are solenoid operated below board) and Facing Point Locks, so the FTP levers are just for show.

Point motors have provision for operating the FPL directly.  Most do it internally to the machine, some did it externally but still operated from the machine.  The impact of that is that there wouldn’t be a separate FPL lever in the box.  The point lever would be painted black (bottom) and blue (top) to show it operated both functions.

 

That leaves me a few more ‘spare’ switches to use (!).

 

2 hours ago, Rick-H said:

It is very good of you to offer to correctly renumber the signal box and I would like to take you up on the offer. Would it be easer for you if I make the changes above and give you a revised drawing?

It’s the sort of thing I enjoy doing.  Probably easier if I have a go first and put my thoughts on here then you can see if you like it and Mike can tell me where I’m wrong!

Paul.

[The Stationmaster]

One thing about numbering Paul.  if it is being numbered as a lever from then usual Western convention applies.  If  it being numbered for switch operation in connection with a panel - what the WR called MES (Minimum Electric Signalling I think it stood for) although it is really a 1980s thing although there were one or two small switch panels in the '70s which might have followed this convention(?) the numbering was done in a different way.  These panels were in some respects OCS by a different name (and they didn't use normal OCS circuitry as far as I know) so were basically a sort of route setting panel.

[5BarVT]

2 minutes ago, The Stationmaster said:

One thing about numbering Paul.  if it is being numbered as a lever from then usual Western convention applies.  If  it being numbered for switch operation in connection with a panel - what the WR called MES (Minimum Electric Signalling I think it stood for) although it is really a 1980s thing although there were one or two small switch panels in the '70s which might have followed this convention(?) the numbering was done in a different way.  These panels were in some respects OCS by a different name (and they didn't use normal OCS circuitry as far as I know) so were basically a sort of route setting panel.

I remember Little Mill I think from D.O. days.  Gut feel is that is was more IFS than OCS.

Or in plainer English for others.

OCS is One Control Switch (Newcastle, York and Cowlairs are those that I have visited) where one switch sets the route (i.e. moves the points) and clears the signal.

IFS is Individual Function Switch where each point and signal has its own switch but you need to set the points first before clearing the signal switch and the signal clears for whichever way the points have been set.

Paul.

[St Enodoc]

9 hours ago, 5BarVT said:

OCS is One Control Switch

Also On Company Service, of course. If you flashed your OCS pass you could get 1p off a cup of tea at Crewe (but not coffee!).

[The Stationmaster]

9 hours ago, St Enodoc said:

Also On Company Service, of course. If you flashed your OCS pass you could get 1p off a cup of tea at Crewe (but not coffee!).

Then they started changing the names of the various station outlets after the management buyout and no longer gave the OCS discount - crafty lot.

[5BarVT]

And back to modelling :-)

I've come up with a numbering sequence that I think would reflect a GWR mechanical box that had had the outside equipment converted to electrical.

I have also given the levers names based on the style of Penzance which was all electrical by mid 80s and included the leads (levers that needed to be operated first).

 

220721 Yeovil Town Model Numbering.pdf

 

I'm a little dubious about 10/20/22 especially 20: from the bay (19) I believe it would be called Starting even though it's on the 'home' side of the box but I've called 22 home as its on a 'through' line even though there is no starting signal beyond 11 points.  20 causes me a problem as I don't like Up Main Inner Home, nor Down Branch Inner Home so I've gone for Starting to Down Main even though it is the through route from Down Branch.

There are options for 10 and 17 as I've seen leads which ignore points which can be both ways (an equivalent of 10 at Penzance which also reads 4 ways has leads in the style of |6|or|Nil|or|14) which is also correct but doesn't make it clear that there are 4 possible routes.

Perhaps Mike can mark my homework.

Paul.

 

[Rick-H]

Paul,

Thanks again, your a star.

I'll have a detailed look over the weekend and get back to you.

 

Rick

[The Stationmaster]

Paul,

 

I'm a bit confused over 10 but it seems you used the original point numbering instead of your new numbering -  you'll quickly see what I mean I'm sure and once 11 and 12 are substituted for 6 and 8 respectively I'm in agreement.  17 is ok by me.

 

BTW the drawn lie of 18 does not agree with the leads, 6 &21 would both lock 18 and it would lead 5.

 

21 technically could have two routes - is that required?

 

22 is straightforward - Down Main Inner Home as you have already named it. The fact that it is also a section signal is irrelevant - just think of a ';box witha single stop signal which is in rear of the 'box.

 

20 is a problem - agreed (as is 13 because it is confusingly named implying it is an Up direction signal   Make 13 D/A or Sub at 20 to Up Main LoS  (see comment below re use of the term Draw Ahead)

Back to 20 -  It would be either 'Up Main Down Inner Home' or as you have named it - which is far less of a mouthful so sounds better even if it might not be quite right.   The only debatable point is the position of the word 'starting' as that would normally come last in the lever lead so both 19 & 20 need to be amended to reflect that, as do No.6. & No.4.  

On the lead reading downwards it should be  line (the signal applies to), movement which only applies if it reads to another line,  function (e.g Home etc).

 

An interesting is the use of the term 'Draw Ahead' or 'Subsidiary'.  The meaning of Draw Ahead in the Rules changed variously over the years but generally the sub is referred as 'Sub' or 'Subsidiary' or even by the 1980s as 'position Light' on notices.  Technically none of the subsidiary position lights here are actually Draw Ahead signals because they read to a different route from the main aspect so I think the should be referred to as 'Subsidiary'

 

That's all that immediately comes to mind or stands out to me

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[RailWest]

Ought there not perhaps to be another main stop signal (as the section signal) on the Down Martock in advance of crossover 11, assuming that there will be occasions when you will be shunting in/out of the Down Siding and the engine yard? Also, without such a signal, shunt 15 is then controlling access into the block section ahead....

[Rick-H]

Paul,

Rainy day, so more time on my computer.

I have updated my master drawing with all your changes. Please do not bother about the red/green dots on each point, these are drilling markers for the control panel LEDs and likewise the boxes with “TC”, these are electrical connections for the model, none of them will show on the final Signal Box drawing.

 

If you would not mine could you please check I have correctly interpreted all the changes?

 

As in the past, I have a few questions.

I do not understand why you have called signal 22 “Down Main Inner Home”, as signals 19, 20, 3 & 4 are all “Starters”. I would have thought that a SR train from Junction to Martock would arrive at platform 3 (SR side of station) and start from there via signal 22.

 

Also I do not know where to position signal 23 “Down Branch Home to Down Main”. My understanding is that a WR train from Mill to Martock would arrive at platform 2 (WR side of station) and start from there via signal 20 to the Down Main.

 

In addition you have me foxed by your “starting even though it's on the 'home' side of the box”. I thought that “starting & home” related to the track and direction of train movement. It shows that trying to learn something as complicated as signalling” from websites is not easy LOL.

 

Your “leads” are a great help to me in trying to write the interlocking for the signals, however I do not understand the leads for signal 10 (the 6 or 6 8 part).I thought it would be 11 or 11 12 or Nil or 14, is that correct?

 

Whilst trying to get my drawing as correct as possible I thought I would replace all the images of the signals with the correct symbol. So having searched the web again I have come up with the following. Are they correct for the period mid 50s to mid 60s?

 

Again thanks for helping a complete novice.

 

Rick

[Rick-H]

All,

Sorry just posted my reply to Paul and the screen refreshed to show Mike's and Chris's posts, so my post is out of order.

Rick

[The Stationmaster]

1 hour ago, RailWest said:

Ought there not perhaps to be another main stop signal (as the section signal) on the Down Martock in advance of crossover 11, assuming that there will be occasions when you will be shunting in/out of the Down Siding and the engine yard? Also, without such a signal, shunt 15 is then controlling access into the block section ahead....

Why add another signal - all it could possibly do is allow a train to pass the platform end signal and creep along to the next one?  true that would enable a platform to be cleared foa following trains but is the place going t o be that busy.

 

Incidentally what is wrong with a GPL controlling access into the section in advance?   Interestingly we went though exactly that discussion when carrying out a SPAD Risk assessment on the proposed signalling just outside a major London terminus where there was siding from which freight trains would be timetabled to depart.  The only problem with using a GPL in those circumstances is that the Driver would be proceeding cautiously and slowly, ready to stop should he see any sort of obstruction ahead - all the way to the next signal capable of showing a red aspect.  The situation here is no different from that and all the lack of a main aspect does is increase the time a move staring from a GPL ought to take get to a signal in advance capable pf showing a red aspect and if the move is a shunt it is never going to go that far anyway. 

 

50 minutes ago, Rick-H said:

Paul,

Rainy day, so more time on my computer.

I have updated my master drawing with all your changes. Please do not bother about the red/green dots on each point, these are drilling markers for the control panel LEDs and likewise the boxes with “TC”, these are electrical connections for the model, none of them will show on the final Signal Box drawing.

 

If you would not mine could you please check I have correctly interpreted all the changes?

 

As in the past, I have a few questions.

I do not understand why you have called signal 22 “Down Main Inner Home”, as signals 19, 20, 3 & 4 are all “Starters”. I would have thought that a SR train from Junction to Martock would arrive at platform 3 (SR side of station) and start from there via signal 22.

 

Also I do not know where to position signal 23 “Down Branch Home to Down Main”. My understanding is that a WR train from Mill to Martock would arrive at platform 2 (WR side of station) and start from there via signal 20 to the Down Main.

 

In addition you have me foxed by your “starting even though it's on the 'home' side of the box”. I thought that “starting & home” related to the track and direction of train movement. It shows that trying to learn something as complicated as signalling” from websites is not easy LOL.

 

Your “leads” are a great help to me in trying to write the interlocking for the signals, however I do not understand the leads for signal 10 (the 6 or 6 8 part).I thought it would be 11 or 11 12 or Nil or 14, is that correct?

 

Whilst trying to get my drawing as correct as possible I thought I would replace all the images of the signals with the correct symbol. So having searched the web again I have come up with the following. Are they correct for the period mid 50s to mid 60s?

 

Again thanks for helping a complete novice.

 

Rick

 

 

The naming of  22 is in accordance with standard GWR/WR semaphore running signal nomenclature.  Stop signal in rear of the signal box are all Home Signals  except those signalling the departure of trains from bay platforms.  all signals in advance of the 'box are Starting Signals.  Plu sof course if thee is more than one signal in either category they will get the advantage of a prefix such as 'Inner' (Home - e.g 22) or 'Advanced' (Starting - e.g. 5/6)

 

The decision about in rear or in advance of the 'box is measured from the longitudinal centre of the 'box so you can have a signal opposite one end of the 'box structure named appropriately to its position in relation to the centre of the 'box.

 

Most of the rest you will now know from my reply to Ian.  As far as the interlocking is concerned you can work out some it backwards from the levers leads - at least where conditional locks are involved, but overall I think you are best advised to start from scratch and although the Western was a bit different with some of its locking a good starting point would be the basic 'rules' of interlocking and the layout, Western style of a locking chart (the one linked below was actually for Hedford but your interest needs to be the style and column headings plus the bits where brackets are used - they are how conditional locks are shown on a chart)

https://www.s-r-s.org.uk/html/gwe/S3434-3.pdf

 

As far as locking rules are concerned keep it simple and I always find to a lot easier if you start with -

1.  Points should be interlocked with each other to prevent conflicting routes being created - example crossover 14 will lock crossover 11, and vice versa, because they create conflicting routes (but 8 and 11 won't lock each other because they can create parallel routes)

2a. Points are interlocked with signals to prevent signals being operated when points are not correctly set. Example Signal 1 locks points 8, 11, and 12 because they would create routes which conflict with that signal.  and of course they also all lock the signal to ensure that it cannot be cleared if they are not set correctly.

2b. In addition locking between points and signals will also involve the point lever when reversed releasing a signal lever.  Example 12 releases 2 (and 2 locks 8 and 11).  Example 8 releases 7 and 9.

 

3. The most difficult one to puzzle until you are used to it is where conflicting signals lock each other.  thinking about the way they work with the point locking although 1, 2 and 7 all conflict with each other there is no need ona model railway for those levers to lock each other because the setting of the various points does that.  But 7 conflicts with 9 and the less obvious one is that 20 &13 conflict with 3 (because a train can't go in both directions at the same time.

 

4. This leads us into conflicting locking where certain situations are created by the setting of points - conditional locking.  Using 10 as an example it will always conflict with 15, 19, 20, & 22 but it will only conflict with 13 if lever 11 is standing reverse (13w11R).  And - forgetting the matter of overlaps which are, in many respects, really overkill on a model railway = 13 will only conflict with 24 if 11 and 14 are standing normal (24with11N 14N) and it will conflict with 17 if 11 and 14 standing normal and 16 is standing reverse (17with 11N 14N 16R).

 

Hope that helps to give you a gentle start.

[Harlequin]

Hi Rick,

How far along are you with the actual layout build?  Would you be open to comments about the track plan?

 

[5BarVT]

7 hours ago, The Stationmaster said:

I'm a bit confused over 10 but it seems you used the original point numbering instead of your new numbering -  you'll quickly see what I mean

Oops!  I did the leads from the original diagram then updated to new (or so I thought).

 

7 hours ago, The Stationmaster said:

BTW the drawn lie of 18 does not agree with the leads, 6 &21 would both lock 18 and it would lead 5.

Oops again.  I assumed that normal was the double line to Junction.

 

5 hours ago, Rick-H said:

Also I do not know where to position signal 23 “Down Branch Home to Down Main”. My understanding is that a WR train from Mill to Martock would arrive at platform 2 (WR side of station) and start from there via signal 20 to the Down Main.

Mea Culpa again!  You said that you didn’t need the move from Branch to Down Main but I thought I would leave space for it should you discover you wanted it later.  But I didn’t amend the diagram to fit.  23 would control the junction indicator on 21 if you added it.  When I first had the idea the lever (switch) was lower down the frame and moving everything about would have been a right pain.  But on reflection, right at the end it isn’t a bother and it could even be 24.  To the knowledgeable it would be clear that it had been added as an afterthought: which would be what had actually happened!!!

 

7 hours ago, The Stationmaster said:

On the lead reading downwards it should be  line (the signal applies to), movement which only applies if it reads to another line,  function (e.g Home etc).

I copied the style from Penzance which is line, function, movement.

But I’ve looked further and found both styles - Exeter West is my style, Westbury North is as you have it.  Parson St is a mixture, generally your style for brasses and mine for ivorines.  You discover something new everyday.

Once again, was that a policy change or difference of opinion between D.O. sections/districts etc?  We’ll probably never know.

7 hours ago, The Stationmaster said:

An interesting is the use of the term 'Draw Ahead' or 'Subsidiary'.  The meaning of Draw Ahead in the Rules changed variously over the years but generally the sub is referred as 'Sub' or 'Subsidiary' or even by the 1980s as 'position Light' on notices.  Technically none of the subsidiary position lights here are actually Draw Ahead signals because they read to a different route from the main aspect so I think the should be referred to as 'Subsidiary'

Agreed as to none being true Draw Ahead.  But again, as taken from Penzance where Position Light is reserved for stand alone shunts and draw ahead is used for all associated with a main aspect, none of which are true D/A.  The only true D/A at Penzance are into the platforms and they don’t appear on the leads because they are a common lever with the main aspect.

Once again, it appears that ‘rules’ were there to be broken!!

 

 

7 hours ago, The Stationmaster said:

20 is a problem - agreed (as is 13 because it is confusingly named implying it is an Up direction signal  

 

I had also wondered about using ‘backing’ to signify wrong direction thus 13 Backing Up Main to LoS.  Would that work?

 

Paul.

Edited July 22, 2022 by 5BarVT
Adding 13 altered lead.

[The Stationmaster]

I'm not over keen on the 13 backing to Up main idea although if it had replaced a similarly configured semaphore signal that is exactly what it would be doing.  But backing signals ceased to be installed in new work from January 1950 so we are then talking about the wording that would have been used with a ground (or elevated) disc so it wouldn't have been called 'backing' any more.

 

The different order of wording on leads s an interesting area where - as you say - we might never know.  The brass lead I have is in the order I explained (I don't know where it came from apart from a pile of non-ferrous scrap).  The Drawing Office Instructions have quite a lot of pages dealing with numbering of levers and different arrangements for numbering levers that operate pointwork but nothing at all about naming on leads and I know that the drawing only covers the typeface and size of letters and there's nothing on it about form of wording.  I only know of one person still around who might know but I think she mainly did signal box diagrams and she has in any case retired (I'm assuming that she might still be around)