Crediton signal box

[Cowley]

A couple of questions that I've been meaning to ask for a while:

I was wondering if anyone knows why Crediton signal box has managed to survive for so long unlike so many other boxes in the area?
Is it a remnant of the once busy stone traffic to Meldon quarry and is it in any way under threat of closure now that the stone traffic has ceased?
I was also wondering where (excluding preserved ones and also excluding Okehampton box) the nearest working original or mechanical signal box on the network is to Crediton nowadays?
Thanks all.

 

[Railsigns]

It has survived because it's responsible for controlling all train movements as far as Barnstaple and not just the immediate area around Crediton.

 

[Right Away]

I was also wondering where (excluding preserved ones and also excluding Okehampton box) the nearest working original or mechanical signal box on the network is to Crediton nowadays?
Thanks all.

For Mechanical boxes I would suggest Yeovil Pen Mill if heading eastwards or Liskeard if heading westwards. There are plenty as you head through Cornwall.

Surviving boxes equipped with panels are Exmouth Junction (rebuilt in 1959 so not technically the original) and St Andrews Junction, as well as some in Cornwall.

Puxton and Worle box remains but only now as a crossing box overseeing Huish and Puxton and Worle crossings.

 

[Cowley]

Thanks for the above replies.
Thinking then about Crediton box controlling the line up to Barnstaple, when the new Exeter panel went fully operational in the 80s why wouldn't they have passed the control of the branches to Barnstaple/Okehampton to that bearing in mind all the other lines that it controlled in the area?

 

[takno]

For Mechanical boxes I would suggest Yeovil Pen Mill if heading eastwards or Liskeard if heading westwards. There are plenty as you head through Cornwall.

Surviving boxes equipped with panels are Exmouth Junction (rebuilt in 1959 so not technically the original) and St Andrews Junction, as well as some in Cornwall.

Puxton and Worle box remains but only now as a crossing box overseeing Huish and Puxton and Worle crossings.

Paignton also has a panel doesn't it?

 

[Railsigns]

Thinking then about Crediton box controlling the line up to Barnstaple, when the new Exeter panel went fully operational in the 80s why wouldn't they have passed the control of the branches to Barnstaple/Okehampton to that bearing in mind all the other lines that it controlled in the area?

To control the Barnstaple line from Exeter panel would have implied a conventional resignalling, at a price too high to justify for such a lightly used branch.

The No-Signalman Token Remote system introduced in 1987 meant control of the whole line could be concentrated into one signal box, Crediton, at a price consistent with the line's status.

 

[plymothian]

Paignton also has a panel doesn't it?

Yes. Paignton box controls the Torbay line from Preston Sands through to Goodrington sidings, taking in Paignton North and Paignton South crossings.

Crediton is the token handover and control for the North Devon line, the Okehampton line as far as Okehampton station, and Credition level crossing.

Exmouth Junction controls the Waterloo lines from Exmouth Junction to Crannaford, the Exmouth line and numerous level crossings.

The rest is controlled by Exeter Panel from Rattery through to Athelney/Fordgate.

Theoretically, they could all merge into Exeter PSB, but with the current set up there are probably too many level crossings for 1 box to watch over. Plus, the token for Eggesford cannot be issued at St David's.

Crediton is going 24 hours, but with [cost heavy] resignalling of the North Devon & Okehampton, could theoretically close.

 

[Cowley]

To control the Barnstaple line from Exeter panel would have implied a conventional resignalling, at a price too high to justify for such a lightly used branch.

The No-Signalman Token Remote system introduced in 1987 meant control of the whole line could be concentrated into one signal box, Crediton, at a price consistent with the line's status.

That makes perfect sense, thanks Railsigns.

 

[Cowley]

Yes. Paignton box controls the Torbay line from Preston Sands through to Goodrington sidings, taking in Paignton North and Paignton South crossings.

Crediton is the token handover and control for the North Devon line, the Okehampton line as far as Okehampton station, and Credition level crossing.

Exmouth Junction controls the Waterloo lines from Exmouth Junction to Crannaford, the Exmouth line and numerous level crossings.

The rest is controlled by Exeter Panel from Rattery through to Athelney/Fordgate.

Theoretically, they could all merge into Exeter PSB, but with the current set up there are probably too many level crossings for 1 box to watch over. Plus, the token for Eggesford cannot be issued at St David's.

Crediton is going 24 hours, but with [cost heavy] resignalling of the North Devon & Okehampton, could theoretically close.

Hi Plymothian. I hadn't heard the bit I've put in bold before. Why is it going 24 hours then? Also are there plans to resignal both lines, would it all have to be altered if the Okehampton line has a regular service anyway?

 

[plymothian]

Because of plans for an earlier and a later train to Barnstaple, Okehampton service, and Network Rail access.

Okehampton signalling won't change with the introduction of the trial service, but should the second Devon "Dawlish avoiding" line be complete, it will have to.

The NSTR signalling is one of the few instances in the Network Rail system in use, and virtually no-one in NR knows anything about it! If the Tarka Line is to achieve the aspirations that it's RUG is fighting for, there will need to be significant changes.

 

[Cowley]

Because of plans for an earlier and a later train to Barnstaple, Okehampton service, and Network Rail access.

Okehampton signalling won't change with the introduction of the trial service, but should the second Devon "Dawlish avoiding" line be complete, it will have to.

The NSTR signalling is one of the few instances in the Network Rail system in use, and virtually no-one in NR knows anything about it! If the Tarka Line is to achieve the aspirations that it's RUG is fighting for, there will need to be significant changes.

Interesting stuff thanks for that. I may have to look up these aspirations when I get a minute...

 

[JN114]

To control the Barnstaple line from Exeter panel would have implied a conventional resignalling, at a price too high to justify for such a lightly used branch.

The No-Signalman Token Remote system introduced in 1987 meant control of the whole line could be concentrated into one signal box, Crediton, at a price consistent with the line's status.

To be fair, Crediton itself as well as Exmouth Jn and Paignton were resignalled during Exeter MAS. The NSTR north of Crediton was so they didn't have to put in expensive power supplies at Eggesford.

At the time of the Exeter MAS scheme in the 80s the intention was for Crediton, Exmouth Jn and Paignton to be controlled from the Panel box at Exeter; but there wasn't the technology to transmit CCTV images in a secure a safe way for the remote level crossings over the distances involved - particularly Paignton (x2) and Topsham crossings. As a crossing box would therefore have to be retained anyway they saw no point re-controlling those areas to Exeter.

You can't expand the current Exeter panel as the controller boards for the TDM are hard wired for the particular Interlockings they remotely control (unlike more modern, modular designs) - any alterations to the TDM would require the whole thing testing from scratch; and would involve lengthy and costly engineering block to do so.

 

[Cowley]

To be fair, Crediton itself as well as Exmouth Jn and Paignton were resignalled during Exeter MAS. The NSTR north of Crediton was so they didn't have to put in expensive power supplies at Eggesford.

At the time of the Exeter MAS scheme in the 80s the intention was for Crediton, Exmouth Jn and Paignton to be controlled from the Panel box at Exeter; but there wasn't the technology to transmit CCTV images in a secure a safe way for the remote level crossings over the distances involved - particularly Paignton (x2) and Topsham crossings. As a crossing box would therefore have to be retained anyway they saw no point re-controlling those areas to Exeter.

You can't expand the current Exeter panel as the controller boards for the TDM are hard wired for the particular Interlockings they remotely control (unlike more modern, modular designs) - any alterations to the TDM would require the whole thing testing from scratch; and would involve lengthy and costly engineering block to do so.

Interesting. I remember when Topsham box was closed (around 1987?), is the level crossing operated from Exmouth Junction now then?

 

[Nippy]

Ive also heard from a colleague who works Exeter PSB and Crediton that there are plans for stone traffic to possibly resume from Meldon.

 

[plymothian]

Interesting. I remember when Topsham box was closed (around 1987?), is the level crossing operated from Exmouth Junction now then?

Yes via CCTV.

 

[Cowley]

Thanks for all the replies folks, I feel a lot more informed now.

 

[MarkyT]

To be fair, Crediton itself as well as Exmouth Jn and Paignton were resignalled during Exeter MAS. The NSTR north of Crediton was so they didn't have to put in expensive power supplies at Eggesford.

At the time of the Exeter MAS scheme in the 80s the intention was for Crediton, Exmouth Jn and Paignton to be controlled from the Panel box at Exeter; but there wasn't the technology to transmit CCTV images in a secure a safe way for the remote level crossings over the distances involved - particularly Paignton (x2) and Topsham crossings. As a crossing box would therefore have to be retained anyway they saw no point re-controlling those areas to Exeter.

There was a limit for approved CCTV transmission technology at the time but I don't think even Paignton would have exceeded it. Silk Mill near Taunton exceded all of these sites in disatnce from Exeter PSB, at just under thirty miles.

I think the decision to keep the local boxes was for other reasons including workload and the token issuing requirement in the case of Crediton. Paignton North was wastefully resignalled twice in the space of a few years. Firstly the North signalbox was abolished and control of signalling and crossing transferred to South signal box, remaining mechanical, with CCTV supervision. Then South signalbox was abolished and a new relay interlocking provided worked by the new small panel in the booking office. The original idea in Area Manager days was for the signaller job to be combined with that of booking office retail, but that never happened for various reasons and was soon superseded by privatisation anyway.

Exmouth Junction was a special case. It was intended to be a pilot site for a new VDU based precursor to IECC with relay interlockings, but the technology was not ready so a 'temporary' wooden NX panel was constructed instead with printed paper graphics beneath a perspex surface. I don't know if that is still there today, but it was in 2009: https://www.flickr.com/photos/salisburyasc/6802586188/

The experimental VDU based system was manufactured but for reasons known only to those involved in the project was never considered suitable for installation. It remained as a demonstration sytem for IECC type operation in the S&T training school at Reading for many years, but I don't know of its final fate upon closure of that establishment.

You can't expand the current Exeter panel as the controller boards for the TDM are hard wired for the particular Interlockings they remotely control (unlike more modern, modular designs) - any alterations to the TDM would require the whole thing testing from scratch; and would involve lengthy and costly engineering block to do so.

Not quite. The hardware was and is a problem but the system at Exeter was more than a traditional TDM and presents additional challenges for certain parts of the control area. It was an experimental 'panel processor', where instead of hard wired relay logic the panel push button controls and indications were handled by a microprocessor based system requiring programming and data preparation. It was an early model of a particular series that was almost immediately discontinued by its manufacturer, and crucially its data configuration methods were no longer supported or offered. Hence following commissioning to the original layout requirement, no further software or site specific data upgrades could be carried out on areas of the panel that use the technology. The more local interlockings at Exeter St Davids itself, Cowley Bridge, Central and City Basin are not affected by this as the panel interface is conventionally hard wired using relay logic that can be altered if required by any suitably qualified signalling design house. These interlockings are remote controlled by large multi-pair cables rather than multiplexed transmission equipment. To the west, more distant interlockings at Dawlish Warren, Teignmouth, Newton Abbot and Totnes use the panel processor system with TDM transmission, as do Tiverton Junction, Silk Mill, Taunton and Cogload to the east. Improvement of the signalled connection to the West Somerset Railway to meet full passenger standards had to await the replacement of Silk Mill Level Crossing by the overbridge there today. This was because site specific data could not be recompiled for additional channels so channels previously used for the level crossing controls had to be reassigned and 'hacked' by external relay logic to become the new route setting controls and indications that were required...

 

[Railsigns]

Exmouth Junction was a special case. It was intended to be a pilot site for a new VDU based precursor to IECC with relay interlockings, but the technology was not ready so a 'temporary' wooden NX panel was constructed instead with printed paper graphics beneath a perspex surface. I don't know if that is still there today, but it was in 2009: https://www.flickr.com/photos/salisburyasc/6802586188/

That's an OCS panel (One Control Switch).

 

[Cowley]

There was a limit for approved CCTV transmission technology at the time but I don't think even Paignton would have exceeded it. Silk Mill near Taunton exceded all of these sites in disatnce from Exeter PSB, at just under thirty miles.

I think the decision to keep the local boxes was for other reasons including workload and the token issuing requirement in the case of Crediton. Paignton North was wastefully resignalled twice in the space of a few years. Firstly the North signalbox was abolished and control of signalling and crossing transferred to South signal box, remaining mechanical, with CCTV supervision. Then South signalbox was abolished and a new relay interlocking provided worked by the new small panel in the booking office. The original idea in Area Manager days was for the signaller job to be combined with that of booking office retail, but that never happened for various reasons and was soon superseded by privatisation anyway.

Exmouth Junction was a special case. It was intended to be a pilot site for a new VDU based precursor to IECC with relay interlockings, but the technology was not ready so a 'temporary' wooden NX panel was constructed instead with printed paper graphics beneath a perspex surface. I don't know if that is still there today, but it was in 2009: https://www.flickr.com/photos/salisburyasc/6802586188/

The experimental VDU based system was manufactured but for reasons known only to those involved in the project was never considered suitable for installation. It remained as a demonstration sytem for IECC type operation in the S&T training school at Reading for many years, but I don't know of its final fate upon closure of that establishment.



Not quite. The hardware was and is a problem but the system at Exeter was more than a traditional TDM and presents additional challenges for certain parts of the control area. It was an experimental 'panel processor', where instead of hard wired relay logic the panel push button controls and indications were handled by a microprocessor based system requiring programming and data preparation. It was an early model of a particular series that was almost immediately discontinued by its manufacturer, and crucially its data configuration methods were no longer supported or offered. Hence following commissioning to the original layout requirement, no further software or site specific data upgrades could be carried out on areas of the panel that use the technology. The more local interlockings at Exeter St Davids itself, Cowley Bridge, Central and City Basin are not affected by this as the panel interface is conventionally hard wired using relay logic that can be altered if required by any suitably qualified signalling design house. These interlockings are remote controlled by large multi-pair cables rather than multiplexed transmission equipment. To the west, more distant interlockings at Dawlish Warren, Teignmouth, Newton Abbot and Totnes use the panel processor system with TDM transmission, as do Tiverton Junction, Silk Mill, Taunton and Cogload to the east. Improvement of the signalled connection to the West Somerset Railway to meet full passenger standards had to await the replacement of Silk Mill Level Crossing by the overbridge there today. This was because site specific data could not be recompiled for additional channels so channels previously used for the level crossing controls had to be reassigned and 'hacked' by external relay logic to become the new route setting controls and indications that were required...

I'm having an acronym nightmare here MarkyT.
What are:

IECCs?
NX panels?
Traditional TDMs?

I think I'm struggling with my lack of signalling education right now (I've pulled a few levers in the past and that's about it).

 

[MarkyT]

That's an OCS panel (One Control Switch).

Indeed! I think there was a further curiosity regarding this installation that may help explain this. ISTR the relay interlockings were designed using standard BRB 'yellow book' circuitry rather than the 'E10K' circuits traditionally used on the WR, including the contemporary Exeter PSB controlled areas. As they were intended to work with the prototype 'IECC lite' rather than a panel, they would have omitted the 'push button ring' relay circuitry necessary for NX operation, because the equivalent functionality would have been incorporated in the computer based solution. To avoid having to retrofit this circuitry, OCS would have provided a simpler 'temporary' interface.

 

[MarkyT]

I'm having an acronym nightmare

IECC: Integrated Electronic Control Centre
An early computer based control centre system using VDU screens and a tracker ball to set routes.

NX: eNtrance eXit system
Panels where routes are set by sequencially operating switches at the start and end of a desired route on the layout diagram, as compared to:

OCS: One Control Switch system
Panels where a single panel switch is assigned for each route in a similar way to individual levers in a mechanical frame

TDM: Time Division Multiplex
A remote control system used to allow large numbers of individual control functions and indications to be transmitted to and from a remote interlocking using only two cable conductor pairs. The technique used is described here: https://en.wikipedia.org/wiki/Time-division_multiplexing

 

[Railsigns]

OCS: One Control Switch

Panels where a single panel switch is assigned for each route in a similar way to individual levers in a mechanical frame

No, an OCS panel is quite different from levers in a mechanical frame. On an OCS panel, just turning a single switch sets a whole route. That doesn't happen when you pull one lever in a frame!

There is a type of control panel whose operation is equivalent to that of a mechanical lever frame. It's termed an IFS panel: Individual Function Switch.

 

[Cowley]

Whilst looking into all of this I found a couple of quite interesting photos:

1 - 158794 heading onto the Exmouth branch with Exmouth Junction box in the background in the late 80s/early 90s taken by David Tozer.
2 - A 150 stopping at Crediton box to swap tokens on the way to Exeter, taken by Graham Boden in 2014.

Worth sharing I thought.

 

[Cowley]

Indeed! I think there was a further curiosity regarding this installation that may help explain this. ISTR the relay interlockings were designed using standard BRB 'yellow book' circuitry rather than the 'E10K' circuits traditionally used on the WR, including the contemporary Exeter PSB controlled areas. As they were intended to work with the prototype 'IECC lite' rather than a panel, they would have omitted the 'push button ring' relay circuitry necessary for NX operation, because the equivalent functionality would have been incorporated in the computer based solution. To avoid having to retrofit this circuitry, OCS would have provided a simpler 'temporary' interface.

IECC: Integrated Electronic Control Centre
An early computer based control centre system using VDU screens and a tracker ball to set routes.

NX: eNtrance eXit system
Panels where routes are set by sequencially operating switches at the start and end of a desired route on the layout diagram, as compared to:

OCS: One Control Switch system
Panels where a single panel switch is assigned for each route in a similar way to individual levers in a mechanical frame

TDM: Time Division Multiplex
A remote control system used to allow large numbers of individual control functions and indications to be transmitted to and from a remote interlocking using only two cable conductor pairs. The technique used is described here: https://en.wikipedia.org/wiki/Time-division_multiplexing

Thanks for that. I may need to look at this with a fresh mind tomorrow though...

 

[MarkyT]

No, an OCS panel is quite different from levers in a mechanical frame. On an OCS panel, just turning a single switch sets a whole route. That doesn't happen when you pull one lever in a frame!

There is a type of control panel whose operation is equivalent to that of a mechanical lever frame. It's termed an IFS panel: Individual Function Switch.

You got me again! IFS is the direct analogue to non route setting lever operation I agree. I should have qualified that OCS is the equivalent of the signal clearance function of typical lever operation. There were a few route setting lever frames in history, although they never caught on, at least in UK. The GWR experimented with such technology at Newport and Winchester Chesil. It requires switched power operated point movement, by air or electric machine for example.

 

[Cowley]

You got me again! IFS is the direct analogue to non route setting lever operation I agree. I should have qualified that OCS is the equivalent of the signal clearance function of typical lever operation. There were a few route setting lever frames in history, although they never caught on, at least in UK. The GWR experimented with such technology at Newport and Winchester Chesil. It requires switched power operated point movement, by air or electric machine for example.

Well it's an easy mistake.