Theatre Indicator box - Which letters / numbers to use?

[WolfofBadenoch]

I'm hoping someone can advise on how numbers and letters are chosen for theatre indicator boxes are chosen. Is it random, platform numbers or some other method?

 

My signal would be approaching a  through / junction station with 3 platforms and a loop - would 1,2,3,L be appropriate?

 

What would the normal distance be for the signal before the 1st point?

 

Thanks

[St. Simon]

Hi,

 

A Threatre indicator would indicate a platform number (e.g. '1' for Platform 1 etc...) or a letter that would be an abbreviation of a section of track (e.g. 'U' for Up line) or a route at a junction  ('B' for the line to Bell Isle out of Kings Cross for example)

 

Yeah, that selection  for your set up seems perfectly logical and I can't see a problem with it.

 

I can't really give you a proper answer about distances, because it varies with location, line speed, speed of diverging route and others, but I would say that it would be far enough away for a train travelling at line speed could pass the signal and slow down to the diverging junction speed before the point. However, I'm by no means an expert so I'll leave that to someone else to confirm!

 

Hope this helps!

 

Simon 

[Torr Giffard LSWR 1951-71]

Hello there,

 

At Derby station (1980s) for example a southbound train may get a 'W' for the Birmingham route. 'W' for Western.

 

Leaving Manchester Piccadilly in the 80s an 'E' would be displayed for trains routed via Ashburys. 'E' for Eastern.

 

Cheers

 

Dave

[LNERGE]

I thought i'd have a look at what i had on theatre type indicators.. I think there will be some head stratching when i come to use one..

 

 

 

[Grovenor]

 

but I would say that it would be far enough away for a train travelling at line speed could pass the signal and slow down to the diverging junction speed before the point.

The train must slow for the diverging junction before passing the signal, in most cases there would be a speed check (by timed occupation of track circuits) such that the train must have slowed to diverging speed before the signal would clear for a diverging route. The position would depend on the track layout and the type of signalling, for multi-aspect signals there is an overlap required of 200 yards for 4 aspect and 300 yards for 3 aspect. It would be preferred that a train standing in the platform is clear of the overlap, but if other conflicting moves are likely the signal may be far enough back so the points are clear of the overlap. Unless you have a very large layout overlap lengths need to be shortened in proportion to most of the distances on the layout if you want your signals to be on scene.

Some examples here http://www.norgrove.me.uk/signalli.htm

Regards

Keith

[Grovenor]

 

I thought i'd have a look at what i had on theatre type indicators..

That looks just like the old Metrovick series type we used in Zambia, on the LMR I had only used ones with the lamps in parallel, the parallel version needed complex lamp proving to check that lamp failures did not result in misleading indications. The series type are easy as they work like the proverbial Christmas tree lights and as the current is constant for any indication lamp proving is very simple, although I see your circuit doesn't have any.

Regards

Keith

[LNERGE]

That looks just like the old Metrovick series type we used in Zambia, on the LMR I had only used ones with the lamps in parallel, the parallel version needed complex lamp proving to check that lamp failures did not result in misleading indications. The series type are easy as they work like the proverbial Christmas tree lights and as the current is constant for any indication lamp proving is very simple, although I see your circuit doesn't have any.

Regards

Keith

I fear the transformer is a beast that will be hard to come by. It looks like it can be tapped just about anywhere?

[flyingsignalman]

You don't mention the type of signalling you are using but in semaphore signalling the signal would be placed to protect pointwork or fouling movements.

 

The inner home at New Brighton protected the crossover at the entrance to the station.

The left hand arm controlled movements to the down sidings.

 

A view from the signal.

 

The box diagram, the routes provided by the indicator are shown.

These photos were taken on 6/9/1989, during the time the box was being reconditioned following a fire when all the track circuits were out of use (We had a supervisor in the box to keep an eye on us instead!)

[Grovenor]

 

I fear the transformer is a beast that will be hard to come by. It looks like it can be tapped just about anywhere?

The lamps were 6v rated, hence in theory there could be taps every 6V up from the minimum of 7 lamps for a 1. My recollection is that the transformers only had the tappings actually needed by the specific indicator, ours were all single sided so managed, had a 110V supply tap and outputs up to about 120. All your voltages are doubled up by having two indicators in series so only need tappings at 12V intervals, (less a bit of course to ensure they are underrun.

Regards

Keith

[beast66606]

The train must slow for the diverging junction before passing the signal, in most cases there would be a speed check (by timed occupation of track circuits) such that the train must have slowed to diverging speed before the signal would clear for a diverging route. The position would depend on the track layout and the type of signalling, for multi-aspect signals there is an overlap required of 200 yards for 4 aspect and 300 yards for 3 aspect. It would be preferred that a train standing in the platform is clear of the overlap, but if other conflicting moves are likely the signal may be far enough back so the points are clear of the overlap. Unless you have a very large layout overlap lengths need to be shortened in proportion to most of the distances on the layout if you want your signals to be on scene.

Some examples here http://www.norgrove.me.uk/signalli.htm

Regards

Keith

 

I'm not sure what you are saying here Keith - approach controlled signals for diverging routes I understand, but then I get lost.

 

Overlaps are to permit a train to run up to the signal without any checking at the previous signal but the routing signal could be at the toe of the very first point, there is no requirement for it to be 200yds from the points, there are plenty of examples where signals are not 200yds from the conflicting route and therefore trains are held/checked at the previous signal, there are also some places have reduced overlaps due to the low PSR which could further complicate matters.

 

For a model the signal could be at or very near the toe of the points.

[Gwiwer]

I agree with beast here.  Route indicators are sited at the signal immediately protecting the diverging routes which can be right up to the points.  The overlap required will depend upon a number of factors including sighting, overall line speed, required approach speed for each possible route, whether or not any route leads to a stop block or is a move permitted to "call-on" a train into a partially-occupied road.  On my own layout I have junction signals which would be barely twenty feet from the tip of the point blades they protect and while that is very close indeed (not least considering the situation is also downhill) there are precedents in the real world.

 

Approach-controlled signalling may be used to progressively lower the speed of an approaching train to that permitted for its signalled route such that the driver may sight a succession of caution aspects ahead and the junction signal and route indicator will not clear until speed is proven to be no higher than the required maximum.

 

What may be displayed on a theatre-type indicator?  In theory anything.  Line or platform numbers are quite common.  Alphabetic line indications are sometimes obscure such as the "B" (for Belle Isle") already cited for Kings Cross above.  While the "W" for Western at Derby isn't altogether obvious either the route does at least lead off to the west.

 

Your proposed platform numbering would be fine and if you also have a non-platform through road then it may be assigned its own number (not also being a platform number) or a letter such as "T" for Through, "L" for Loop or indeed what ever you want.  Some locations display two letters such as "UM" or "UR" for Up Main / Up Relief as in the Thames Valley.  

 

You may assign what ever letter and give it what ever meaning you wish.  

[TheSignalEngineer]

Overlaps are to permit a train to run up to the signal without any checking at the previous signal but the routing signal could be at the toe of the very first point, there is no requirement for it to be 200yds from the points, there are plenty of examples where signals are not 200yds from the conflicting route and therefore trains are held/checked at the previous signal, there are also some places have reduced overlaps due to the low PSR which could further complicate matters.

Facing points in an overlap are no real problem, indeed there are many 'Swinging Overlaps' where the facing points can be moved with a train approaching the signal provided certain conditions are met. As for the distance between the signal and first facing points, on the LMR this was usually 120ft in mechanical points and 60ft in power points to allow time for the points to completely go over if they started moving and the train ran by the signal. If closer than these distances then controls could be put on using the berth track circuit to the signal.

 

 

What may be displayed on a theatre-type indicator?  In theory anything.  Line or platform numbers are quite common.  Alphabetic line indications are sometimes obscure such as the "B" (for Belle Isle") already cited for Kings Cross above.  While the "W" for Western at Derby isn't altogether obvious either the route does at least lead off to the west.

 

Your proposed platform numbering would be fine and if you also have a non-platform through road then it may be assigned its own number (not also being a platform number) or a letter such as "T" for Through, "L" for Loop or indeed what ever you want.  Some locations display two letters such as "UM" or "UR" for Up Main / Up Relief as in the Thames Valley.  

 

You may assign what ever letter and give it what ever meaning you wish.  

Nowadays geographical indications are generally not used. The preferred ones would be platform numbers or M-Main, F-Fast, S-Slow, B-Branch, G-Goods. Combinations where misreading could occur should be avoided such as 8 and B, or 5 and S on the same indicator.

 

Where there are complex layouts such as bidirectional running or multiple roads on station approaches these could be qualified by indications such as UM or DM, or letters to match the line names such as A, B, C, and D roads. Subsidiary and shunt aspects have between 1 and 3 characters to defind the destination of the move.

[WolfofBadenoch]

Thanks for all the answers :-)

 

It's answers my initial queires but just incase it makes any differences here's somemore details - the layout is mid - late 80's, WCML (practices) in Scotland, planned with 4 aspect signals. Each of the 4 routes would be bi directional through the station area.

[AberdeenBill]

A classic example of a mechanical indicator box under a semaphore was on platform 3(?) southbound at Exeter St Davids, which could show "UP CEN" (to Exter Central) or "DN MAIN" (towards Plymouth).

 

Bill

[big jim]

Nowadays geographical indications are generally not used. The preferred ones would be platform numbers or M-Main, F-Fast, S-Slow, B-Branch, G-Goods. Combinations where misreading could occur should be avoided such as 8 and B, or 5 and S on the same indicator.

 

Crewe has some anomolies which you have mentioned as to be avoided, CE105 and CE107 on the down slow and fast can show B8 to go into one of the south end bays, heading south you can get W which directs you towards the shrewsbuy line as well as P to take you to the potteries but L to take you towards the potteries loop line which are side by side

 

Also coming from the north on the fast (and iirc the slow too) the theatre indicator to take you into platform 5 shows a route indicator "flash" type indication but if you are going any other route requiring an indication it will show a letter.

 

It was resignalled last in 1985 though!

[Flying Pig]

The train must slow for the diverging junction before passing the signal,

The other way sounds more fun...

[TheSignalEngineer]

Crewe has some anomolies which you have mentioned as to be avoided, CE105 and CE107 on the down slow and fast can show B8 to go into one of the south end bays, heading south you can get W which directs you towards the shrewsbuy line as well as P to take you to the potteries but L to take you towards the potteries loop line which are side by side

 

Also coming from the north on the fast (and iirc the slow too) the theatre indicator to take you into platform 5 shows a route indicator "flash" type indication but if you are going any other route requiring an indication it will show a letter.

 

It was resignalled last in 1985 though!

I also put a few up myself at West London Junction where I had some double width boxes made for the South West Sidings job. There get to be places where you need so many indications that you have to resort to place names, but this is the second option rather than the first. At Crewe F & S would be used for the Fast and Slow lines to Stafford. P was used for the Stoke line as it is called the Up & Down Potteries line. I wonder if the Salop line was ever called the Whitchurch line?

 

The B8 at Crewe is probably to remind the driver that 8 isn't a through road.

[Gwiwer]

Another example there (Crewe) of using letters which are not immediately obvious to a casual observer.  "W" I might have got for "Western" or "Whitchurch" although the Chester line also deviates broadly to the west.  "P" for Potteries is much less obvious even with a little geographic knowledge unless one also knows the line is known as the "Potteries" by rail staff.  Using "S" for Stoke might have been confused with South i.e. the WCML.

[big jim]

i've always understood the "W" to stand for "Western"

 

coming from the north you can get L for the loop between platform 11 and 12 and then get another L from there to take you towards the "Potteries Loop Line"

[big jim]

Here is an example of a "local" theatre indicator, not a fantastic picture as the signal is so bright and i was stood in the platform at the time

 

 

Any guess' as to where i was heading to?

[beast66606]

Chiltern lines ?

[big jim]

No

 

The clue is that signal is the north end of hatton station

[TheSignalEngineer]

I thought it was Hatton but couldn't recall what the new signal had on it. Must be Claverdon.

[big jim]

One like for the signalengineer for getting it right!

 

I suppose they wanted to avoid an S for Stratford to stop confusion with slow (even though there isnt one!)

[TheSignalEngineer]

One like for the signalengineer for getting it right!

 

I suppose they wanted to aboid an S for Stratford to avoid confision with slow (even though there isnt one!)

Or B for Branch which could have been confused with Birmingham.