Signals - Present-Day Semaphore, Lights and Repeaters

[Michael Hodgson]

24 minutes ago, St Enodoc said:

Excellent training video and well done both to the instructor and trainee. I have to say that the duster technique needs a little more work though!

They didn't cover making entries in the book though !

[Pacific231G]

Can anyone offer a simple explanation of how a single line key token or tablet machine pair "knows", in completely foolproof/failsafe way that a token has been withdrawn and also how it knows that it has been replaced in one or other machine to free it? I assume it's some sort of electromechanical device that locks both machines but I've never seen the sort of explanation that one can find for block indicators.

Just to add to that, how does it work when you add an intermediate token machine?  There used to be one at Fort William that enabled a driver with a token to enter the goods and loco yard sidings and place the token in the machine when clear of the running line thus enabling another train to receive a token (the intermediate key token machine could only hold a single token)    

 

In about 2000 I filmed the whole single line procedure operating on the LBNGR for a video I produced about the railway before they went over to radio control but, though I understand what it did, I never did find out how it did it. I think their machines went to the Severn Valley line but AFAIK they weren't interlocked with any signalling since the LBNGR only had a shunting disk at Page's Park. 

[TheSignalEngineer]

Simplisticly the instruments all have to be in phase, i.e. in the same state to give a release. Replacing a token in any instrument puts them back on phase.

There are some explanations posted here. Click on the top and middle pictures to download the documents. They onclude some basic layouts and wiring diagrams.

https://dickthesignals.co.uk/home/heritage-signalling-information/brb-training-manual/operation-of-single-lines.html

[Michael Hodgson]

Essentially the instruments contain an electrically operated lock which is operated by a pulse from the far end. 

There is a commutator within the mechanism that is turned by extracting (or re-inserting) a token.

So you can only get one out if the commutators at each end are correctly synchronised, and it doesn't matter which end wants one, but if either end has extracted a token, the instruments will be out of phase and you can't get another until it is returned to one of the instruments.   Electric Train Staff, Tablet and Key Token instruments all work on this same  principle.

 

In the case of a No.3 Tablet instrument, the token can't be returned to the instrument that issued it because of the physical design of this instrument, so it has to travel through the section.  Identical-looking No 6 Tablet instruments don't suffer this handicap.

 

Because it is operated by a pulse rather than the continuous current of most double line block instruments, the indications will remain correct even if the line wire breaks while there's a train in section.  Though until the lineman has fixed it, you can't run any more trains without changing to a different system of control (usually this is appointing a pilot man, who acts as a train staff in human form, travelling on the trains)

 

At a wayside siding, you might require the token to unlock the ground frame, uncouple leaving most of the train on the main line, attach or detach a couple of  wagons with the token locked into the ground frame while you do this.  You then re-couple your train and continue your journey, leaving the ground frame set for the main line, which is necessary to retrieve the token.  This can all be done mechanically and doesn't require an intermediate instrument, BUT you can't shunt the train clear and allow other trains to run through because you've still got the token.

 

Alternatively, if there is an intermediate instrument intercepting the line wire, you can shut a train in, and insert the token into the instrument once the section is again clear.  This enables the intermediate instrument to put the instruments at either side to back into phase.  To get the train back out again, if the instruments are in phase (there is no train in the section), a token can be extracted to allow you to oprate the points and let the train out of the siding again.  The process of getting this release requires co-operation of both signalmen.

 

You can also have an auxiliary instrument, useful in places where the signalman would have a long walk to hand the token to the driver.

In this case, the signalman obtains a token from the adjoining box in the usual way, but instead of giving it to the driver, he inserts it into another instrument which is connect to the suitably located auxiliary instrument, and doing this releases a token for the train crew to extract.  The downside of this is that the auxiliary only ever issues tokens while there is an accumulation of tokens in the assoicated instrument in the signalbox.  So after a number of trains, the line man will have to remove the build-up and transfer the tokens to restock the auxiliary.  Alternatively where arriving trains don't pass the box an auxiliary can be used to collect tokens, with a similar rebalancing need.

 

You can also have No Signalman Key Token instruments, where one end is worked by the train crew, or No Signalman Token Remote where both ends are worked by the train crew under supervision of one box (such as the passing loops on the Esk Valley line to Whitby).  I don't think His Majesty to had to work the instruments for the Royal Train to come off that line onto the NYMR the other day though - perhaps one day they'll train him!

 

https://www.railsigns.uk/info/etoken1.html

 

 

[Pacific231G]

Thank you both for your replies. The system I saw in use on the LBNGR was I think a "No signalman" key token system but I don't know if the instrumets were Tyers no 3  or no 6. I'm sort of seeig an analogy with the system where two switches control a light (typically on the ground and first floor and the light is only on when both are switched to the same wire. In this case the switches can only be changed by withdrawing or replacing a token (The system is obviously more complicated than that but that would be how I'd understand being in or out of phase)  and of course it uses pulses rather than a continuous current but those pulses cannot do anything unless the instruments are in phase. I may of course have completely got the wrong end of this particular stick!

[Rugd1022]

Now long gone, Saltey and Washwood Heath, installed in 1969 I think...

 

 

 

Moreton-in-Marsh...

 

 

 

 

 

 

 

 

 

[Michael Hodgson]

1 hour ago, Pacific231G said:

Thank you both for your replies. The system I saw in use on the LBNGR was I think a "No signalman" key token system but I don't know if the instrumets were Tyers no 3  or no 6.

I can't remember clearly but I thought Leighton Buzzard used RETB though that requires special equipment on board each loco, so it was probably something rather more primitive - after all one of their stations is called Stonehenge Works!  But I'm pretty sure they used some form of radio for control of movements.

 

As its name suggests NSKT uses key token instruments whilst No 3 and No 6 are older style tablet instruments.

In the photo below (New Bridge on the NYMR, which controls Pickering Station) the red instrument is a key token instrument whilst the green one is tablet.  Key tokens look like keys, and tablets are flat discs of metal or fibre  (usually round, commonly 4 1/2 " in diameter)

https://en.wikipedia.org/wiki/Token_(railway_signalling)#/media/File:Single_line_tokens.jpg

 

The tablet instrument in the photo works to Levisham, whilst the token instrument is used only when Levisham is closed and the section is all the way to Goathland.  There is locking between the two systems, so that it is only possible to bring the "long section" working in effect when the New Bridge-Levisham and the Levisham-Goathland* sections are both clear of trains and those systems are then locked out of use.

 

 

* worked by yet another (less flexible) method of single line control - Staff & Ticket. 

Trains must either carry the staff or it must be shown to the driver and he must carry a signed ticket instead, the staff travelling on the last train of a series sent in the same direction.

Train tickets are kept in a locked box, which can only be opened when the train staff is there.

 

[St Enodoc]

5 hours ago, Pacific231G said:

I'm sort of seeig an analogy with the system where two switches control a light (typically on the ground and first floor and the light is only on when both are switched to the same wire.

That's exactly right, David.

[Rugd1022]

Not exactly 'present day' but I thought it worth posting this gem from 1972 - double banner repeater at Stratford-upon-Avon station...

 

 

 

 

[The Stationmaster]

On 15/06/2023 at 12:21, Michael Hodgson said:

Video explaining working of signal box with GWR key token instruments, signal box opening procedure, testing single line instruments, use of king lever, running of trains with token exchange, closing box where section signal is locked by the block.

 

 

Hmm,

 

Some interesting things there some of which are rather puzzling but might relate to the way electrical controls have, or haven't been included.  There appears to be no closing switch (but the King Lever could be a switching out lever as is the case on some frames).   I'm not at all sure if stirrup locks were used on Reading frames (someone will no doubt know?).

 

Addendum

Having done a bit of checking I'm fairly sure that the arrangements at Llangollen Goods as it is now has been 'locally engineered' to cater for whatever equipment they were or weren't able to get hold off as it is very different from the normal GWR method. 

The GWR effectively controlled everything through the Switching Out Lever - it controlled the switching of the token circuits and had a circuit controller to ensure that it could not be fully reversed until the through token circuit was proved and had been tested.  Once fully reversed it released the running signals in both direction over. the loop line which was signalled for trains in either direction - including those released by 'Token Out'

 

The 'free' indicators used on signals released by the token are a good idea if a 'box is worked by volunteers who aren't there regularly although I've never seen them anywhere else. it's not very clear hw the electric lock lifts as there's no plunger.   Similarly  I can't quite understand the situation with the FPLs - they seem to have no electric locks but appear to pull rather easily if they are lifting point locking bars - excellently adjusted stuff out on the ground perhaps. (does anyone know?  Has the locking been adapted to somehow work electric locks without a plunger to release them but there also don't appear to be any emergency releases on the FPL levers)  

 

And there is obviously no sequential locking on the running  signals which again suggests to me that things have been done in various ways to get round a lack of electric locks and relays etc

 

And  yes St E - definite need for some duster practice.

 

 

Edited June 16, 2023 by The Stationmaster

[The Stationmaster]

15 hours ago, Michael Hodgson said:

I can't remember clearly but I thought Leighton Buzzard used RETB though that requires special equipment on board each loco, so it was probably something rather more primitive - after all one of their stations is called Stonehenge Works!  But I'm pretty sure they used some form of radio for control of movements.

 

As its name suggests NSKT uses key token instruments whilst No 3 and No 6 are older style tablet instruments.

In the photo below (New Bridge on the NYMR, which controls Pickering Station) the red instrument is a key token instrument whilst the green one is tablet.  Key tokens look like keys, and tablets are flat discs of metal or fibre  (usually round, commonly 4 1/2 " in diameter)

https://en.wikipedia.org/wiki/Token_(railway_signalling)#/media/File:Single_line_tokens.jpg

 

The tablet instrument in the photo works to Levisham, whilst the token instrument is used only when Levisham is closed and the section is all the way to Goathland.  There is locking between the two systems, so that it is only possible to bring the "long section" working in effect when the New Bridge-Levisham and the Levisham-Goathland* sections are both clear of trains and those systems are then locked out of use.

 

 

* worked by yet another (less flexible) method of single line control - Staff & Ticket. 

Trains must either carry the staff or it must be shown to the driver and he must carry a signed ticket instead, the staff travelling on the last train of a series sent in the same direction.

Train tickets are kept in a locked box, which can only be opened when the train staff is there.

 

 

I winder if Leighton Buzzard use simething based on the system devised by and used on the Ratty - which is working to the Controller's order over a radio system.  the Controller hasa train graph showing the booked service, plus any planned additionals, and Drivers call in to report their progress which allows the Controller to update the graph and re=plan any crossing meets.  

 

It's a very good system and all calls are recorded so it heeds a proper  base station, and good operational disciplire.  Each train is given a card before departure noting its planned working and Driver's update that as they go plus they note on the card any revised Instructions from the Controller 

[Michael Hodgson]

26 minutes ago, The Stationmaster said:

The 'free' indicators used on signals released by the token are a good idea if a 'box is worked by volunteers who aren't there regularly although I've never seen them anywhere else. it's not very clear hw the electric lock lifts as there's no plunger.   Similarly  I can't quite understand the situation with the FPLs - they seem to have no electric locks but appear to pull rather easily if they are lifting point locking bars - excellently adjusted stuff out on the ground perhaps. (does anyone know?  Has the locking been adapted to somehow work electric locks without a plunger to release them but there also don't appear to be any emergency releases on the FPL levers)  

 

And there is obviously no sequential locking on the running  signals which again suggests to me that things have been done in various ways to get round a lack of electric locks and relays et

 

Heritage lines do have an issue of trying to run a service with volunteers who aren't there regularly.  Although a line typically runs every weekend during the summer season (and perhaps a few Santa services in winter), you don't necessarily have the same volunteer on duty each weekend.  Also some of the boxes might only be opened for certain busy weekends (diesel gala day, Thomas weekend etc).  Whilst they do need to be qualified to work the box concerned, volunteer signalmen may be asked to cover whichever box needs staffing today, more like a relief signalman on BR.  So there's rarely that detailed familiarity with the box and its idiosyncracies that the full-time BR resident signalman had.  There's a lot to be said for K.I.S.S. in this environment.

 

As for the free light on the starter, that's a desirable feature on equipment that only gets used once in a while, as such things can get sticky and stop working.  When they ring S&T to complain the starter won't clear, S&T (another volunteer, who happens to have the necessary technical knowledge) can ask the idiot question - "Have you got the Free light?" before travelling out to "repair" what might turn out to be a simple user error, while the punters are wondering why their train isn't going anywhere.  The line's Responsible Officer needs to have a good understanding of what practices are safe when (apparent) failures occur.

 

I believe sequential locking is a relatively recent feature in the history of semaphore practice, and can be considered an optional extra.  I think it was useful as part of controls which force the lazy signalman just leaving his running signals all the time rather than restoring after passage of a train, but that isn't an attitude likely to apply to a volunteer.  I was surprised that he was instructed to clear the starter out of sequence, but that does make sense if there is a chance of the (fairly infrequently operated) one-pull circuit dropping out.

 

Heritage lines tend to use whatever relays their S&T are able to scrounge from resignalling schemes on the National Network etc, but these are safety critical devices with a use-by date, just as a boiler has a certificate after which it needs inspection.  You can get expired relays re-certified to prolong their life, but that costs money.  And you need the right type of relay for each particular function, so finding a good stock of appropriate relays in serviceable condition tends to be a problem for S&T.  It can make sense not to implement optional functions unless you can maintain it, with enough spares.

[Michael Hodgson]

23 minutes ago, The Stationmaster said:

I winder if Leighton Buzzard use simething based on the system devised by and used on the Ratty - which is working to the Controller's order over a radio system.  the Controller hasa train graph showing the booked service, plus any planned additionals, and Drivers call in to report their progress which allows the Controller to update the graph and re=plan any crossing meets.  

 

It's a very good system and all calls are recorded so it heeds a proper  base station, and good operational disciplire.  Each train is given a card before departure noting its planned working and Driver's update that as they go plus they note on the card any revised Instructions from the Controller 

I agree that is more likely.  I don't remember their having any fixed signals.

[The Stationmaster]

30 minutes ago, Michael Hodgson said:

Heritage lines do have an issue of trying to run a service with volunteers who aren't there regularly.  Although a line typically runs every weekend during the summer season (and perhaps a few Santa services in winter), you don't necessarily have the same volunteer on duty each weekend.  Also some of the boxes might only be opened for certain busy weekends (diesel gala day, Thomas weekend etc).  Whilst they do need to be qualified to work the box concerned, volunteer signalmen may be asked to cover whichever box needs staffing today, more like a relief signalman on BR.  So there's rarely that detailed familiarity with the box and its idiosyncracies that the full-time BR resident signalman had.  There's a lot to be said for K.I.S.S. in this environment.

 

As for the free light on the starter, that's a desirable feature on equipment that only gets used once in a while, as such things can get sticky and stop working.  When they ring S&T to complain the starter won't clear, S&T (another volunteer, who happens to have the necessary technical knowledge) can ask the idiot question - "Have you got the Free light?" before travelling out to "repair" what might turn out to be a simple user error, while the punters are wondering why their train isn't going anywhere.  The line's Responsible Officer needs to have a good understanding of what practices are safe when (apparent) failures occur.

 

I believe sequential locking is a relatively recent feature in the history of semaphore practice, and can be considered an optional extra.  I think it was useful as part of controls which force the lazy signalman just leaving his running signals all the time rather than restoring after passage of a train, but that isn't an attitude likely to apply to a volunteer.  I was surprised that he was instructed to clear the starter out of sequence, but that does make sense if there is a chance of the (fairly infrequently operated) one-pull circuit dropping out.

 

Heritage lines tend to use whatever relays their S&T are able to scrounge from resignalling schemes on the National Network etc, but these are safety critical devices with a use-by date, just as a boiler has a certificate after which it needs inspection.  You can get expired relays re-certified to prolong their life, but that costs money.  And you need the right type of relay for each particular function, so finding a good stock of appropriate relays in serviceable condition tends to be a problem for S&T.  It can make sense not to implement optional functions unless you can maintain it, with enough spares.

Interestingly Bishops Bridge Box on the SDR - with a much larger frame uses a Switching out Lever and has plungers for all the. electruic locks.

 

Working ling levers where you need to operatea plunger to lift the electric locks is a habit quickly aquired and you son know when it's free once u you're pressing the button  because you can hear the lock drop.

 

I agree that getting hold of electric locks, and particularly circuit cntrollers is not particularly easy but many lines have managed it without too much trouble.  And signalling relays don't have to be shelf type relays although they are definitely better for some functions.   .   I think a lot depends on who is doing the work and their abilities and knowledge.    For example the GWS signalling folk managed to re-lock the double twist Radstock frame something which many professional signal engineers applauded as it is very difficult locking to work with.  And they created a very simple system for locking the frame in various states using different train staffs working Annets Key instrument.  We - completely independently - used a similar method, plus a King Lever, to lock the frame open for one train running at Tyseley when we created the signal box there although in that case locking the frame released the Train Staff.

 

With decent volunteers training someone to work a 30-40 lever frame and understand all the relevant instructions isn't a difficult task but it needs somebody who can carry out that training and act asa. supervisory 'Inspector' snusre that things are done properly.  However as that is what the law (ROGS) requires it shouldn't be a task any railway can stand aside.

Edited June 16, 2023 by The Stationmaster

[Michael Hodgson]

Sorry to say I wasn't aware of the preserved box at Tyseley. 

 

I visited the steam centre a few times when I was still a student and the North Warwickshire line was still properly signalled  ... that would have been 1972!  Seems I'm overdue for another visit.

[Rugd1022]

On 15/06/2023 at 00:25, uax6 said:

 

And I have a claim to fame with it... I spent a day facing off the concrete foundation around the base of this beast after it was erected, with a 1" chisel and lump hammer. I also helped fit the boarding on the landing and the fittings to the dolls... I was young then though...

 

Andy G

 

Interesting stuff Andy! Where did the signal come from...?

 

St.Erth, before the 'cage of potential head injury' was fitted...

 

 

Banbury north before the more recent resignalling...

 

 

Basford Hall Junction, Crewe...

 

 

Knighton Junction, Leicester...

 

 

And a pair of golden oldies at Leamington Spa in the '70s...

 

 

 

[The Stationmaster]

10 minutes ago, Michael Hodgson said:

Sorry to say I wasn't aware of the preserved box at Tyseley. 

 

I visited the steam centre a few times when I was still a student and the North Warwickshire line was still properly signalled  ... that would have been 1972!  Seems I'm overdue for another visit.

We put the 'box in at Tyseley in 1986/87 having the structure recovered from Holesmouth Jcn plus we stripped a large amount of re-usable stuff including parts of the frame, whatever we could find on the blockshelf (the block instruments and bells had gon) plus various parts of nearby signals plus a considerable quantity pf rodding run components and cranks etc.  I also bough 5 tons of channel rodding - in very good to very poor condition - from the Signal Works closing down sale at Woodley and we sold on the poorest stuff to other railways as well as getting rid of some surplus cranks etc that way.

 

I did the signalling plan and locking chart and teh WR Chief Locking Itester made only I m onr alteration to the latter) while he did the electrical control table.  The only thing we had any difficulty with was getting hold ofa circuit controller and  a decent point a macine in good order requirng a minimum of fettling.  Some of the signal were erected with a crane but we moved one 21ft high arm signal  by hand, complete with the concrete weight) because it wasn't quite in the right place -'great fun' that was. 

[Michael Hodgson]

26 minutes ago, The Stationmaster said:

Some of the signal were erected with a crane but we moved one 21ft high arm signal  by hand, complete with the concrete weight) because it wasn't quite in the right place -'great fun' that was. 

 

I wasn't there when they erected this signal post, but I was told that it was done using manpower and a rope or two.

 

Note the mechanical linkage on the crossing gate to alter the angle of the lamp to the gate.  The crossing is on a skew, so the red light needs to shine at an angle when the gate is across the road, but at right angles to the gate when across the line.  Signal box just visible through the coach windows.

 

 

On the other hand, equipment was available for moving some of the signals ... well within its safe working load!

[Michael Hodgson]

1 hour ago, The Stationmaster said:

Some of the signal were erected with a crane but we moved one 21ft high arm signal  by hand, complete with the concrete weight) because it wasn't quite in the right place -'great fun' that was. 

 

We were offered this little signal post, but we had to recover it ourselves.   There was rather more post below ground level than you might expect.  OK, so with help from the winch on the Land Rover we did manage to dig it free, complete with the massive lump of concrete it had been buried in.  With a lot of effort we then jacked it up on stacks of sleepers to put it onto the trailer.  But the wise decision was taken that it would be unsafe to tow that as an overhanging load down the M4 behind the Land Rover, and as far as I know it's still there.

Edited June 16, 2023 by Michael Hodgson

[uax6]

8 hours ago, Rugd1022 said:

 

Interesting stuff Andy! Where did the signal come from...?

 

I can't quite remember, but it was a bit of a home brew. I believe the main post was used for a signal bridge for colour-lights somewhere, and the rest was made at Swithland Sidings. I can certainly remember using a 9" grinder with a wire brush in it to clean the mill scale off parts of the new bit. 

The GCR was quite lucky in that their S&T lads had a lot of contacts with the local BR/Railtrack S&T lads, and one weekend we did a recovery at Derby, from an old goods platform overlooking the south end of the station. It was a haul of a couple of 30-35 foot semaphore posts, and a lot of fittings. It took a fair few of us to lift the post onto the artic trailer!

 

8 hours ago, Rugd1022 said:

 

 

 

I quite fancy making something similar to this for the garden. I've got a Metro-vick Hernia distant head (with a curved sighting board, think full sized Berko!) and a semaphore and post that needs erecting, so would be a good idea to combine the two. Just need a standoff bracket for the hernia to sit on.

 

Andy G

[TheSignalEngineer]

A few of my old friends coming out of the woodwork here!

On 15/06/2023 at 19:16, Rugd1022 said:

Now long gone, Saltey and Washwood Heath, installed in 1969 I think...

Correct about the date, I was involved in testing those.

 

8 hours ago, Rugd1022 said:

Banbury north before the more recent resignalling...

 

Provided during the abolition of Banbury Junction SB (1976 IIRC). The signal was at the end of the Down Goods which prior to 1969 used to go through to Banbury Ironstone box. The underbridge is the Oxford Canal, the Good line span was removed after the Ironstone box closed.

 

9 hours ago, Rugd1022 said:

And a pair of golden oldies at Leamington Spa in the '70s...

Both replaced on my projects before the SSI was done, can't remember the exact ones but the bracket was a signal renewal as a colour light cantilever c1980. I think the Down Starter with the lower colour light distant for the first Saltley signal was replacd by a three aspect diring a remodelling job in the mid 1970s.

12 hours ago, Rugd1022 said:

Not exactly 'present day' but I thought it worth posting this gem from 1972 - double banner repeater at Stratford-upon-Avon station...

I did the plan for closure of the Stratford end of the through route following the derailment at Winchcombe (1976?) which made those signals redundant. I think we did the work at the same time as the conversion from ATC to BR AWS. The ATC ramp for the lower distant by the road bridge in the second picture was the last operational one to be removed from BR lines. 

[uax6]

4 minutes ago, TheSignalEngineer said:

 

 

Both replaced on my projects before the SSI was done, can't remember the exact ones but the bracket was a signal renewal as a colour light cantilever c1980. I think the Down Starter with the lower colour light distant for the first Saltley signal was replacd by a three aspect diring a remodelling job in the mid 1970s.

 

 

So you will be able to tell me how these combined semaphore and colourlight worked....

 

I'm guessing that there was a detector box for the arm, that was adjusted so that when the arm was high enough to obscure the signal lamp (but not necessarily fully off), then the colour light head was turned on? And of course the head was turned off at the same point as the arm returned?

 

Ta

 

Andy G

[TheSignalEngineer]

Just now, uax6 said:

 

So you will be able to tell me how these combined semaphore and colourlight worked....

 

I'm guessing that there was a detector box for the arm, that was adjusted so that when the arm was high enough to obscure the signal lamp (but not necessarily fully off), then the colour light head was turned on? And of course the head was turned off at the same point as the arm returned?

 

Ta

 

Andy G

That's about it. There was a blanking plate in place of the green aspect of the semaphore arm.

[St Enodoc]

7 hours ago, uax6 said:

The GCR was quite lucky in that their S&T lads had a lot of contacts with the local BR/Railtrack S&T lads

At least one of them was/is one of both groups.

[KingEdwardII]

20 hours ago, Rugd1022 said:

double banner repeater at Stratford-upon-Avon station...

Also with a spectacular example of a telegraph pole.