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LED position light signal - mass introduction?

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D Foster

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I'm trying to recall which year it was that there was a massive effort to swap out all the old style position light signals and rapidly replace most of them with the current LED beasties? I think that it may have been 2008? Can anyone help me out with this please?
In a related way... does anyone know when the first LEDs of each signal type started to be introduced please?
:D
 
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MarkyT

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I'm trying to recall which year it was that there was a massive effort to swap out all the old style position light signals and rapidly replace most of them with the current LED beasties? I think that it may have been 2008? Can anyone help me out with this please?

Don't know the date but ISTR mass changeover was justified not only on the basis of lamp life but also operational safety as it allowed the 'ON' aspect to be changed from a white and a red lamp illuminated to two reds. There had been cases in the past where the single red had gone out and drivers had misinterpreted the single white remaining as a proceed aspect. The brighter, more reliable and duplicated reds of the new type were far less likely to suffer even a single lamp out, and the danger of misinterpretation was eliminated.

In a related way... does anyone know when the first LEDs of each signal type started to be introduced please?
:D

The Dorman standard long range LED signal head (i.e not the lightweight one) was the first main head approved I believe. The certificate of acceptance states it was first issued in 2003, which, from my experience, was about when they started to appear in small numbers, often as an attempt to improve sighting of certain problem signals.

http://www.unipartdorman.co.uk/assets/longrange_cls.pdf
 

Crossover

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Don't know the date but ISTR mass changeover was justified not only on the basis of lamp life but also operational safety as it allowed the 'ON' aspect to be changed from a white and a red lamp illuminated to two reds. There had been cases in the past where the single red had gone out and drivers had misinterpreted the single white remaining as a proceed aspect. The brighter, more reliable and duplicated reds of the new type were far less likely to suffer even a single lamp out, and the danger of misinterpretation was eliminated.

Is there any reason why the traditional heads had to have a white and a red rather than two reds for 'on'?
 

ComUtoR

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Additionally, to crossovers question. Why do we still get Red/Whites introduced ? I've noticed a couple upgraded to LED but still remain red/white and I think I saw a new one altogether and that was also a red/white
 

John Webb

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Is there any reason why the traditional heads had to have a white and a red rather than two reds for 'on'?
There could only be three bulbs fitted into the unit; the 'Pivot' bulb was white and the one stop bulb was the red. The 'cleared' third bulb was white to make the 'cleared' position distinct and so that no red bulb was displayed to confuse the issue.

With the compact nature of LED displays, the 'pivot bulb' is a mix of white and red LEDs to give the two-red and two-white display.

At St Albans South box we have one of the older ones set up as a demonstration, although the 110V bulbs that were in it were replaced by 12V 5watt car bulbs to keep the glare down. If you ever get to visit us we'll be happy to show it to you!
--- old post above --- --- new post below ---
Additionally, to crossovers question. Why do we still get Red/Whites introduced ? I've noticed a couple upgraded to LED but still remain red/white and I think I saw a new one altogether and that was also a red/white

It may be for consistency in a particular area where not all the GPLs are being upgraded. It's quite possible that the new GPLs can show two-red and two-white, but are awaiting further changes. (St Albans South box has also recently acquired a fairly new LED GPL, and the red pivot LEDs can be disabled simply by removing two links on the input terminals.)
 
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Crossover

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There could only be three bulbs fitted into the unit; the 'Pivot' bulb was white and the one stop bulb was the red. The 'cleared' third bulb was white to make the 'cleared' position distinct and so that no red bulb was displayed to confuse the issue.

With the compact nature of LED displays, the 'pivot bulb' is a mix of white and red LEDs to give the two-red and two-white display.

At St Albans South box we have one of the older ones set up as a demonstration, although the 110V bulbs that were in it were replaced by 12V 5watt car bulbs to keep the glare down. If you ever get to visit us we'll be happy to show it to you!

Thanks for that John - that makes sense!
 

33056

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I'm trying to recall which year it was that there was a massive effort to swap out all the old style position light signals and rapidly replace most of them with the current LED beasties? I think that it may have been 2008? Can anyone help me out with this please?
IIRC it was early 2005 where I work, on the basis of that is when the entries in our fault book regarding lights out on GPLs dry up.
 

D Foster

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"33056" Any chance of knowing roughly where the area was please?

John (and others)
I have a certain question as to why only three lamps and not four? Presumably someone decided it would be both adequate and cheaper. Although, as suggested, there would be a slight risk with the red lamp failing... So - not the usual 100% fail safe.
I don't know if the incandescent lamp PLGS had twin-filament (one as back-up) lamps in them or if they were provided with a proving circuit?
(I might get a look into an old one sometime soon to at least check the lamp).

I do think that part of the arrangement would be to give a little of an "upper quadrant" effect. Does this make sense?

A little differently there are "ground signals" - both "shunt" and "subsidiary" that had two whites and two reds (or two yellows - although I've never seen that... did they exist?). I've always believed that these were "fibre optic" signals - but I've never got my paws on one to see what's inside... Are they really a fibre optic system?
Does anyone have any idea when they first appeared please?
I've also only ever seen them on LM and Eastern areas... Were they ever on SR or WR please?

Thanks :D:D:D
 

John Webb

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John (and others)
I have a certain question as to why only three lamps and not four? Presumably someone decided it would be both adequate and cheaper. Although, as suggested, there would be a slight risk with the red lamp failing... So - not the usual 100% fail safe.
I don't know if the incandescent lamp PLGS had twin-filament (one as back-up) lamps in them or if they were provided with a proving circuit?
(I might get a look into an old one sometime soon to at least check the lamp).


I do think that part of the arrangement would be to give a little of an "upper quadrant" effect. Does this make sense?

A little differently there are "ground signals" - both "shunt" and "subsidiary" that had two whites and two reds (or two yellows - although I've never seen that... did they exist?). I've always believed that these were "fibre optic" signals - but I've never got my paws on one to see what's inside... Are they really a fibre optic system?
Does anyone have any idea when they first appeared please?
I've also only ever seen them on LM and Eastern areas... Were they ever on SR or WR please?

Thanks :D:D:D
The older GPLs used single filament 110V lamps - I think 20 or 25 watt. It was unusual to 'prove' the lamp - more common to just indicate what position the controlling relay was in.

As far as I am aware, but can't state with certainty, the Two-Red/Two-white GPL was a result of the introduction of LEDs; I've not, so far, come across a mention of fibre-optic use in GPLs, only in Banner Repeaters.
There are a few Two-Yellow/Two-white GPLs in LEDS around, but I'm told their use is discouraged these days.
 

D Foster

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Thanks some more :D
That 5318 signal is the PLGS fibre optic type I know. The Subsidiary / "Draw Ahead" versions simply had blanking plates over the red positions - a similar arrangement to the old filament lamp types that had a blanking plate over the red lens position - when they either had the appropriate letter C, S or W removed or when no letter was fitted from the start.

Would you call the mini lights onP46 "Auxiliaries"?

:D:D:D
 
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