Understanding Signal Box Diagrams

[The Stationmaster]

15 hours ago, Halton Boy said:

Thank you everyone this has been very interesting and I have learned a lot.

Georeferenced maps is my new friend.

These are the stations that I am looking at now:

Thornbury South Gloucester

Fairford

Burnham on Sea

Marlow Bucks

Cinderford

Nailsworth Midland branch South Gloucester

Dursley   Midland branch  South Gloucester

Chesham by Chesham park

Rickmansworth branch L&NWR

Watlington in Oxfordshire  South of Thame.

Stroud Midland branch

Once I have been through these I will take a look at Scotland's branch railways.

A number of those are covered in books, various, so if you find one of real interest it might be worth scouring the 'net to see if there is a book about that station/line.  Worth too looking for models which already exist - for example there is a really nice model of Burnham-On-Sea which reappeared on the exhibition circuit not too long back -

https://sheptonmrs.wordpress.com/burnham-on-sea/

 

This online article about modelling the Watlington branch might be worth a look as, amongst other things, it shows how various books have been used as reference sources -

http://www.gwr.org.uk/nowatlington.html

 

You have come up with a very varied selection with a considerable range of differences between them in both traffics. operation, and - to a lesser extent type of location.  So it might be worth considering also what particular style of location you are interested in.  

 

Finally a gentle word of warning - the railway track layouts shown on 25" Ordnance Survey maps can be erroneous in details.  If anything they  represent the track layout at the time the survey was carried out irrespective of the date shown on the map so the layout can be completely different for a later date.  And buildings - both railway and otherwise can be missing. 

[Michael Hodgson]

2 minutes ago, The Stationmaster said:

And buildings - both railway and otherwise can be missing. 

Sounds like my layout.

[Halton Boy]

Hello Mike

Thank you for the information.

I now understand that every branch line station has been modelled by someone.

What I think I will do is find an interesting track diagram and adapt it to fit. Or I will combine elements from a number of branch terminus.

 

The other important thing I want to do is to fully understand signal box diagrams.

Do I need to understand Locking Tables?

I have found one for Calne station. But I don't fully understand it.

 

Here is a new Highlands Railway signal box diagram:There are still some things that I do not understand:

A

Dock crossover ground frame.  1: AK release

Please could someone tell me what the AK means. 

Lever 1 in the signal box or the staff release the ground frame.

B

Please could someone tell me what this symbol means? It looks like a box on a post.

C

We have seen this before. Lever 9 operates the point off the main line and the two trap points. Lever 10 is the FPL.

D

There is a round object on the side of the signal post.

Please could someone tell me what this is.

Is it a ground signal for the distillery siding mounted on the signal post?

E

Beneath signal post 12 is a symbol like a 4 written backwards.

Please could someone tell me what this is.

Thank you everyone.

[RailWest]

A. I would guess that AK = Annett's Key

B. It's probably a notice board. Probably says 'STOP' or something similar.

C. Correct.

D. Difficult to tell, but looks like a 'D' sign (to indicate that there is a Fireman's Call Plunger provided - see Item 9.6 here https://www.railsigns.uk/sect9page1.html)

E.  It may be a symbol for the FCP, tho' it looks to me more like a symbol for a telephone.

 

 

[Grovenor]

14 minutes ago, Halton Boy said:

Hello Mike

Thank you for the information.

I now understand that every branch line station has been modelled by someone.

What I think I will do is find an interesting track diagram and adapt it to fit. Or I will combine elements from a number of branch terminus.

 

The other important thing I want to do is to fully understand signal box diagrams.

Do I need to understand Locking Tables? Only if you want to, search on here you will find topics on just that.

I have found one for Calne station. But I don't fully understand it.

 

Here is a new Highlands Railway signal box diagram:There are still some things that I do not understand:

A

Dock crossover ground frame.  1: AK release

Please could someone tell me what the AK means.  Annets Key, was explained at some length in one of the posts above. You put the key into GF lever 1 to release the frame, there is one key released from lever 13 in the box and one attached to the staff to use when the box is closed. When the box is open the staff key gets locked into lever 13 to allow the release of the Annets Key from lever 13.

Lever 1 in the signal box or the staff release the ground frame. Actually lever 13 as above

B

Please could someone tell me what this symbol means? It looks like a box on a post. It will be a notice board telling any loco arriving from the siding to stop and await instructions, ie permission to exit, from shunter or from box.

C

We have seen this before. Lever 9 operates the point off the main line and the two trap points. Lever 10 is the FPL. Yes

D

There is a round object on the side of the signal post.

Please could someone tell me what this is.

Is it a ground signal for the distillery siding mounted on the signal post? That is a sign indicating that there is a firemans plunger there, to be used to show train has arrived if signal at stop. No need for signals to use the siding, the GF is released by a key on the staff or token. It seems that the brach is one engine in steam with a staff if box closed and electric token working when box op[en.

E

Beneath signal post 12 is a symbol like a 4 written backwards.

Please could someone tell me what this is. I suspect that is showing the location of the firemans call plunger.

Thank you everyone.

Use expand to see answers.

[5BarVT]

Hi Halton Boy,

All good questions, and in this case an oddity of a box because sometimes it’s a signalbox and sometimes it isn’t!
 

Chris and Grovenor beat me to the answwers!

 

Regarding whether lever 1 reference is in the box or the frame, I can see it both ways as Grovenor has.

(G)WR practice was to put the key into the frame beside the locking (a bit like a mortise lock) but ScR practice was to put the key into a box on a lever which I would expect to be lever 1 on this frame.  So it is entirely logical for the 1: AK Release to refer to the GF.  However, I think it does refer to the box because there are 13 levers all working and nothing else is allocated to lever 1.

 

Which then brings us to the other GF and the oddity.  The other GF is released by the staff and the tablet. The staff release is standard stuff (just the configured end of an Annett’s Key fixed to the staff), in this case the same configuration so that the Dock GF can be operated by both.  The tablet release must be similar but I’m not familiar with such as I come from Token land not Tablet land!

 

I have convinced myself that there two ‘release’ levers in the box, 1 and 13, release in quotes because they do different things. 1 gives a release to the Dock GF, 13 is released by the staff to allow the box to work.  I have been trying to see how things worked when the box was closed - clearly in 1933 there was a need for the loco to run round its train.  The train would arrive with the staff, operate the GF to get into the loop, run down to the box end and use the staff again to release the levers in the box to get back out of the loop.  If a goods train for the distillery, it would shunt on the way in, again using the staff.  My reluctance for this approach is that once the staff is in lever 13 the whole box is available for use, including the tablet instruments by people not trained.

So I then turn to having a porter/signalman: competent to operate the box, including tablet instruments etc. but only required in the box when the train arrived rather than permanently, unless a second train was required down at the terminus at the same time.

Canny these Scots!

My other thought is a reduced version of that, based on something similar used at Wick and Thurso when the boxes had shut but still token working from Georgemas Jn.  If the last departing train were worked by staff (allowing the signalman to cease duty) then the last arriving train could still get the loco onto shed for disposal.  But then, why put the staff release on the distillery frame?

Paul.

 

[Halton Boy]

Hello Chris, Keith and Paul.

AK = the Annets Key.

I did not know that there could be an Annets key on lever 13 in the signal box.

I will read your answers through a couple of times to be sure I know what you have said. Sorry but it has been a long hard day.

I understand the sign at B.

I knew that they had telephones by a signal post, but I did not know about plungers.

Was that an older idea before telephones were common?

Just one more question, if I moved the distillery siding nearer to the station, between signal 11 and 3, to save space, would this affect the signalling? 

I will make up a plan and post it with the changes.

Thank you everyone.

Ken 

[Jeremy Cumberland]

29 minutes ago, 5BarVT said:

My reluctance for this approach is that once the staff is in lever 13 the whole box is available for use, including the tablet instruments by people not trained.

What would the interlock arrangement be?

 

All that appears to be required is for the instrument to be disabled with 13 normal (or whatever position it is in when the staff is out) and for 13 to be backlocked when a token is out, but I have no idea what might have existed in practice, or how the interlocking was done.

 

This is what I have in my mind. Does this make sense?

Insert staff to release 13. Pull 13 (or return normal - I am unclear which way round the lever works). This releases the frame both for shunting and as a signalbox, and also allows the token instrument to be used. Whenever a token is out, 13 is backlocked so it can't be moved. When no token is out, 13 can be moved and the staff removed for staff operation, and the token instrument is disabled.

 

Would moving 13 to release the staff require 2, 3 and 11?

[Corrour]

Folks,

 

Aberfeldy had a dual-system where normal operation would be Train Staff but at times of more traffic a tablet could be used. See BoT Extract:

MT29/95        Aberfeldy

 

'Oct.15, 1946 – Mount reported that in 1938, the LMS decided that the Branch originally worked by tablet could be made to operate train staff with one engine in steam most of the year. Arrangements to introduce the train staff vice the tablet by inserting a king lever at Aberfeldy, which had fixed to it a train staff in shape of an Annett’s Key lock attached to the King Lever No.13, which normally stood pulled. This lever could then be restored to the midway position which allowed the Up and Down running signals to be replaced to normal (danger). Thereafter the King Lever could be fully replaced, removing the back locks from Nos.4 & 10, which could then be placed normal. At the same time replacement of the King Lever to normal permitted the section tablet to be withdrawn from the mechanical control instrument behind the King Lever while the train staff became locked in the King Lever lock. This control instrument was of McKenzie & Holland design, adapted to work in conjunction with the King Lever. When the tablet was locked in the control instrument, the block instruments were out of phase at Aberfeldy and Ballinluig. The main Ground Frame at Aberfeldy had 13 working levers and was controlled by an Annett’s Key.  Another 2-lever Ground Frame worked the Platform run round crossover. There was a 4-lever Ground Frame at the Aberfeldy Distillery and similar 4-lever Ground Frame at Grandtully, both controlled by either train staff or tablet whichever was in use.'

I'm going to attach a couple of drawings of mine showing detail. Note the drawing earlier in thread is an M1 track & signalling NOT an M5 signal box diagram. I attach both.

 

Aberfeldy-M1-1934-Rev.2-rot.pdf Aberfeldy-M5-1947-Rev.0-rot.pdf

[Michael Hodgson]

1 hour ago, Halton Boy said:

Hello Chris, Keith and Paul.

AK = the Annets Key.

I did not know that there could be an Annets key on lever 13 in the signal box.

I will read your answers through a couple of times to be sure I know what you have said. Sorry but it has been a long hard day.

I understand the sign at B.

I knew that they had telephones by a signal post, but I did not know about plungers.

Was that an older idea before telephones were common?

Just one more question, if I moved the distillery siding nearer to the station, between signal 11 and 3, to save space, would this affect the signalling? 

I will make up a plan and post it with the changes.

Thank you everyone.

Ken 

Signals do not necessarily have phones.  Rule 55 requires the fireman to go to the box if his train is held at signals to remind the signalman of its presence (and sign the register as evidence that he has done so), but there are a number situations where we can be saved a long walk.  A diamond plate means the line is track circuited and the signalman is automatically notified that a train is waiting.  A D-shaped plate with a hole in it means there is a firemans call plunger which notifies the signalman when operated - this may be on the signal post itself or nearby.  A plate with "T" on it means there is a signal post telephone he can use instead.  But you would not usually have both, and yes the idea is slightly older.

 

If you move the distillery closer, it may be possible for the signalman to work the associated points and signals, in which the ground frame would be dispensed with.  The key distance is to the signalbox, as there is a restriction on maximum distance for mechanical operation of points by rodding (the limit changed a couple of times as technology improved).  Of course if they fitted a point motor, that does away with the distance limitation.

3 hours ago, Halton Boy said:

The other important thing I want to do is to fully understand signal box diagrams.

Do I need to understand Locking Tables?

 

 

No.  Most modellers don't do the locking, as a model is not safety criticial. 

Nor do you need to understand the locking to understand the box diagram.

 

However it is useful to understand some of the general principles of locking if you want to operate a layout prototypically, as the effects of locking can be simulated by doing things in the right sequence.  Important principles arising from locking include

• set your points before clearing signals (... because the locking would enforce that)
• put the signals back to danger before changing any point that the signal reads over
• before you clear a distant signal, ALL the stop signals for the route must be cleared
• distant must be restored to caution before any of the stop signals
• signals should be cleared in the sequence in which they are passed (sequential locking)
• observe "flank protection" at a double track junction, that is to say first swing points for any conflicting adjacent line so that there is no risk of collision on a diamond crossing
• don't clear signals in opposing directions on the same track at the same time (though this is permissible, indeed required when a box on a single line is switched out of circuit). 
• don't clear main signal and a subsidiary or shunt signal from the same place at the same time (except NER before about 1925)

If you want  to study locking tables, you will find the the Southern Railway often included locking tables data on their signal box diagrams, although it wasn't general practice elsewhere.  Understanding locking tables is a subject of similar complexity to this subject of this thread and I would suggest starting a new topic if you want to take that further.

[Corrour]

For those interest i attach the M2

[Halton Boy]

Hello

Thank you so much for the PDF's and the locking chart.

Do you have PDF diagrams of Penicuik in the 1940's please?

The two stations are similar. One has the up and down sidings and the other has the distillery and engine shed.

Which one will fit the space? Which one has more operating fun?

 

Thank you Michael for the "Important principles arising from locking"

That is what I needed to know, which lever to pull first.

 

I will read through everything tonight and get back to you all.

Was the Annets key in the signal box in an instrument on the shelf which locked lever 13, and not on the lever like the ground frame?

This is really interesting, Thank you everyone. 

 

[Harlequin]

A point of pedantry:

 

This topic is titled "Understanding Signal Box Diagrams" but is actually talking about signalling diagrams.

 

Signal box diagrams are the physical things displayed in signal boxes, which have similar, but different, symbology depending on region and era.

 

[5BarVT]

3 minutes ago, Harlequin said:

A point of pedantry:

That’s the trouble with getting into signalling- we’re all a bit that way inclined.

:-)

Paul.

[RailWest]

>>>... train staff in shape of an Annett’s Key lock attached to the King Lever No.13....

 

Almost certainly then attached to the front of the lever. Once 13 was reversed and the staff (key) was withdrawn from the lock, then the lock bolt would go down into a slot in the frame quadrant to prevent the lever being replaced (well, that's one way of doing it anyway).

[The Stationmaster]

When looking at signalling - and then going on to interlocking 0 there are certauin things you need to understand.

 

1. Although the basic principles of both signalling and interlocking applied to all the main line railways including their branch lines etc there were variations in detail, esoecially in respect of subsidiary and ground shunting signals, between the Companies and some of that extended well into BR days as differences between the Regions.

 

2.  The basic principles for signallinga nd interlocking were established by  what was normally called in shorthand 'the Requirements' whichwent by various titles over the years and were established by legislation for teh safe construction and operation of railways.  these also changed over the years as loopholes were closed or standards were improved.  The example via the first link below is. the 1892 version which was being amended for republication at the 1902 version.  In later years these were published by the Ministry  of Transport with a blue cover

 

https://www.railwaysarchive.co.uk/docsummary.php?docID=166

 

1928 version -

 

https://ekeving.se/ext/uk/Requirements_MoT_1928.pdf

 

Link to 1950 version on this page 

 

https://www.railwaysarchive.co.uk/docsummary.php?docID=4808

 

3.  From these requirements the railways developed their principles for both signalling and interlocking although there was some measure of commonality imposed through the work of the railway Clearing House which decided on 'standard; Rules and Refulations for the various railway companies although all of them then made their own additions and exceptions to/from the RCH standard Rules and regulations.  this then leads you into the various operating publications such as the Rule Book,  Signalling Regulations and General Appendix and so one which explain all of that for the use of operating staff.  these too changed gradually over the years

 

 

 

 

[Corrour]

Halton Boy will see what I have for Penicuik :-)

[Michael Hodgson]

2 hours ago, Harlequin said:

A point of pedantry:

 

This topic is titled "Understanding Signal Box Diagrams" but is actually talking about signalling diagrams.

 

Signal box diagrams are the physical things displayed in signal boxes, which have similar, but different, symbology depending on region and era.

 

Valid point.  This site has a very large collection of real signal box diagrams, mostly East Anglia.

https://www.flickr.com/photos/pwayowen/

 

To take a few examples, the Dereham South Junction diagram has a couple of white patches - these would be alterations to reflect changes on the ground; additions would often just be added to an existing diagram but a piece of paper stuck over something that has been removed.  The style in which the signal box itself is drawn differs from that used in the diagrams in this thread - the St Andrews cross doesn't necessarily imply a pyramid roof.

 

Shepreth is close to the style used further up in the thread, but note the distant arms under signals 27 and 4 shown hollow rather than yellow (meaning worked by another box) and in two positions (indicating that it is slotted, and in three positions on under signal 3 (indicating that is slotted more than one way) - note that a gate box is shown which works the right hand level crossing, but it is not a block post and would be manned by a crossing keeper - less skilled and lower paid than signalman.

 

Hopton shows the the style drawn by the contractors who built the box - note the date in the bottom right.  Signal box position shown by the red box at the end of Down platform.  The black blocks are their way of showing the normal lie of points; note that there are no facing points because the Board of Trade discouraged them, trains had to reverse into refuge sidings to be overtaken by faster traffic.

 

A gradient diagram such as that shown next was usually also exhibited in the box, information useful in emergency if you become aware of a train becoming divided

 

Chesterton junction - the ovals in the track are cut-outs for a bulb which lights up when the track is occupied.  The extent of these track circuits is shown by the alternate streches of blue and yellow (mostly Down Line), green and brown (mostly Up line), and they are identified by the letter beside the lamp. Track in black is not track circuited.  This box has a mixture of semaphore, 3- and 4-aspect colour lights, disc and position light signals.  Miniature colour light signals used for admission of trains from Ely to Up Goods Loop (10) or to Reception Sidings (8).  Mechanical FPLs are worked by a separate lever so both numbers are shown by the point/FPL; FPLs are built into the point motors for the electrically worked ones, so only one lever is used.  Detonators in front of the box worked here not by a lever but by stirrups.  Unusually here, the former Up Branch is out of use so all trains must run through the Up Branch loop instead.

 

East Rudham - M&GN style diagram.  5 & 13 are mechanical fouling bars, locking the loop points so that you can't let a train out of the other line if a vehicle is too close to the convergence.  19 & 20 are wicket gates by the level crossing which is on a slight skew.  The gong (12) would be used by the signalman to summon porters from other duties when a train was imminent.

 

 

West Holmes.  Much more modern diagram, angular style track all drawn as stright lines.  Track circuits indicated by little red lights (two, in case of bulb failure)  Covers a bigger geographical area, supervising a lot of level crossings - some CCTV with full barriers, some Automatic Half Barriers (AHBs) some User worked (UWC).  Rule 55 exemption diamonds on signal posts where line is track circuited.  Some levers work a stop signal and a two-aspect Y/G repeater.  "Lever worked for Interlocking" refers to equipment which has been removed (for example a former siding), but the signalman still has to pull the levers as though it were still there because the associated locking has not been changed.

 

 

Gradient Diagram - coastal line from North Walsham to Cromer.  And you thought Norfolk was flat!  The vertical scale is of course exaggerated compared to the horizontal.

 

Lowestoft - a series of drawings, apparently produced in planning changes, but it shows not only the layout and signalling, also the pull plates (which are fitted to each lever telling you what other levers the locking requires you to pull first) and including diagrams of the much simpler ground frames, complete with their locking

 

 

Edited January 26, 2023 by Michael Hodgson

[The Stationmaster]

13 minutes ago, Michael Hodgson said:

Valid point.  This site has a very large collection of real signal box diagrams, mostly East Anglia.

https://www.flickr.com/photos/pwayowen/

Lowestoft - a series of drawings, apparently produced in planning changes, but it shows not only the layout and signalling, also the pull plates (which are fitted to each lever telling you what other levers the locking requires you to pull first) and including diagrams of the much simpler ground frames, complete with their locking

 

 

They are drawings for an alterations scheme - new work coloured red is the normal convention on such drawings.  Basically they are a further use of what is nowadays called a Signalling Facilities Drawing.

 

Incidentally another point about signal box diagrams is that the drawing style varied not only from company/Region to company/Region but in some cases even between different drawing offices in the same company.  And of course like everything else the styles and detail shown changed over the years!

[Corrour]

Here's Penicuik M1

[RailWest]

I like the idea of a "Stationary" distant - do they have some then which wander about ? :-)

[Halton Boy]

Hello everyone

I am sorry that we have moved away from signal box diagrams into signalling and other matters. 

I am learning all the time with your help.

I can now look at a signal box diagram and know what a lot of it means and why it is shown.

There are some things that I am not clear about:

With Penicuik does the signal box lever 13 have a Annette's key box fixed to it or is it a separate box on the shelf behind the levers, because I cannot find a picture of a lever in a signal box with a key box on it. 

Ground frame levers have the key box fitted.

Would lever 13 be a ground frame release and be painted blue over brown?

A king lever is a lever which is released by another box and so lever 13 was not a king lever.

I will get back to signal box diagrams soon.

 

[RailWest]

Like so many things S&T, 'it varies' between railway companies, different periods etc etc.

 

>>>With Penicuik does the signal box lever 13 have a Annette's key box fixed to it or is it a separate box on the shelf behind the levers, because I cannot find a picture of a lever in a signal box with a key box on it. 

 

I doubt the former, as how then would the 'instrument' lock the lever? I would suggest that you assume the latter.

 

>>>Ground frame levers have the key box fitted....

Some do, others have it attached to the interlocking tray.

 

>>>Would lever 13 be a ground frame release and be painted blue over brown?

There was no 13 at Penicuik :-) Do you mean 1? Again, the answer might vary depending upon whether pre- or post-Grouping. 

 

>>>A king lever is a lever which is released by another box....

Not necessarily so. Certainly the one at Aberfeldy was not.

[Halton Boy]

Hello

Thank you very much for the diagram for Penicuik.

I have just realised looking at your diagram that signal 10 controls access to the down line sidings.

I though it was for access to the up line sidings. That's because the signal is on the left of the track. Oh dear!

 

I now realise to access the up line sidings the engine would pull into the platform and run round the wagons by using the loop.

The points 4 would be changed for the main line and the engine would back on to the wagons and then pull the wagons forward past the starter signal 2.

The points 4 would be changed for the loop and the engine would shunt the wagons into the up sidings.

This same sort of procedure would be used for the down sidings with the engine pulling the wagons forward past the home signal 8 and onto the main line.

How does the engine driver know how far he can shunt down the main line past the signal box?

Would there be a limit of shunt sign on the main line?

 

In operating a model I would like to move wagons from the down sidings to the goods shed and the up sidings and vice a versa.

Did they assemble a freight train in the platform line or in the goods yards.  I suppose it would depend on the length of the platform line and the sidings and if a passenger train was due.

 

I now have three interesting branch station layouts to work on.

But I am confusing myself with the three stations as well.

 

I have come a long way in my understanding thanks to all your help everyone.

Ken

 

 

[RailWest]

>>>Would there be a limit of shunt sign on the main line?..

 

Unlikely IMHO. The purpose of a LoS was to limit wrong-direction movements, which by definition do not exist on a bi-directional single-line. (Ignore what you may see on some heritage lines :-) ) The signalman would authorise the driver to shunt into the single-section only as far as was necessary, and as the driver would not have the staff/tablet in his possession at that time anyway then he could not proceed to go all the way to the next block post.