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Co-Acting signals

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Jack Barry

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Can anyone explain what exactly Co-Acting signals are for, I know they use them still on the north end of the Met and they were at quite a few locations years before on the Met again now being used as well for T/Ops to do with Spads.
 
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Dstock7080

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Co-actors are also used for signal-sighting issues, where it would be too difficult/expensive to move the original signal and wiring, a new co-acting signal is placed.
eg. Tower Hill, Whitechapel, Aldgate East, West Kensington.
 

bluegoblin7

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Co-actors are also used for signal-sighting issues, where it would be too difficult/expensive to move the original signal and wiring, a new co-acting signal is placed.
eg. Tower Hill, Whitechapel, Aldgate East, West Kensington.

Notable examples also include Baker Street platform 6 and Hammersmith (Met) platform 2, both to accommodate S7 trains.
 

edwin_m

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The definition of a co-acting signal is a second signal head close to the main one that displays the same aspects. They are provided where for some reason the main signal head can't be easily seen from all the positions it must be viewed from.

It's not the same as a repeater, which is located on the approach to a stop signal and displays a different aspect.
 

baz962

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End of Gunnersbury platform as apparently the original single signal was hard to see.
 

philthetube

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Does anyone know the reason for the co actors heading for Chesham on the single track. They are certainly not for sighting issues.
 

bramling

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There is the Chesham single line entry signal and a co-acter around 10m distance from it.
No one (Alive/working) actually knows the reason for it!

Indeed - I don't think anyone knows why it was done like that.

It may have been due to it marking the entry to a single line, so someone thought it was a good idea to put it there as an additional mitigation measure. However this isn't the full story, as other single lines didn't / don't have the same treatment. The only difference at Chalfont is that the signalling is in a multi-aspect layout, although again that doesn't really answer the question of why.

It may well remain one of life's mysteries!
 

Lrd

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There's a few at Queens Park too
Only the one co actor at Queen's Park, the northbound station starter (BB32). The rest are draw ups.

Theres another co actor installed only a couple of months ago at Piccadilly Circus southbound thanks to the new stopping mark.
 

philthetube

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There is the Chesham single line entry signal and a co-acter around 10m distance from it.
No one (Alive/working) actually knows the reason for it!
I did hear a tale that the two signals were controlled from the boxes at Chesham and Chalfont, and that both had to be green to allow the train to proceed, I suppose that that makes more sense but have no idea if correct.
 

Dstock7080

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The co-acting signalling at Chalfont has only been installed since Amersham cabin took control of the area, my guess is 10-20yr ago.
 

Ex LT

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The co-acting signalling at Chalfont has only been installed since Amersham cabin took control of the area, my guess is 10-20yr ago.
JW83 as it was coded but later recoded to JT83 has been there since 1959 and before that when there was a mechanical box at Chalfont JT25 in 1955!! Coming from Chesham JV17 in 1949 and later JT69B in 1970.
 

rebmcr

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I did hear a tale that the two signals were controlled from the boxes at Chesham and Chalfont, and that both had to be green to allow the train to proceed, I suppose that that makes more sense but have no idea if correct.

If that were the case, it would not be described as a co-actor?
 

bramling

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JW83 as it was coded but later recoded to JT83 has been there since 1959 and before that when there was a mechanical box at Chalfont JT25 in 1955!! Coming from Chesham JV17 in 1949 and later JT69B in 1970.

Was the co-acting signal there before 1959?

I had a look at the relevant yellow peril last night, which seems to give the impression the co-acting signal was installed from new at that time. It doesn’t give any reason for its existence though...

Would there have been non-tripcock-fitted BR trains running up there at that time? If so it would certainly have been an added safeguard against a train ending up on the single line and then disregarding the first signal, particularly if for example it was unlit. All speculation though...

There certainly wasn’t any co-acting signal provided at Finchley Central nor Epping - however these both date from different times (1940s versus late 1950s), and neither are a multi-aspect area like the Met.
 

Harsig

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Was the co-acting signal there before 1959?

I had a look at the relevant yellow peril last night, which seems to give the impression the co-acting signal was installed from new at that time. It doesn’t give any reason for its existence though...

There certainly wasn’t any co-acting signal provided at Finchley Central nor Epping - however these both date from different times (1940s versus late 1950s), and neither are a multi-aspect area like the Met.

Co-acting signals of this configuration were first installed at Chalfont (JT25 & JT25 Co-Acting) and Chesham (JV17 & JV17 Co-Acting) in April 1949. This was in connection with the continuous track circuiting of the Chesham branch, which allowed the existing electric train tablet installation to be taken out of use. At the time these were the only colour light signals in the Chalfont and Chesham areas (aside from the Chalfont up single line distant and a repeater for JV17 (RJV17) which were both installed at the same time).

When the Chalfont area was resignalled ten years later in 1959 JT25 & JT25 Co-Acting were removed and replaced by the current pair of signals (JW83 & JW83 Co-Acting) approximately 500-600 feet further from Chalfont. When control of the Chalfont area was transferred to Amersham Cabin in 1960 these two signals were renumbered to JT83 & JT83 Co-Acting.

In 1970, when Chesham signal cabin was closed, JV17 & JV17 Co-Acting were renumbered to JT69B & JT69B Co-Acting, and these signals were only removed when the track circuits on the Chesham branch were replaced by an Axle Counter in the early 1990s.
 

bramling

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Co-acting signals of this configuration were first installed at Chalfont (JT25 & JT25 Co-Acting) and Chesham (JV17 & JV17 Co-Acting) in April 1949. This was in connection with the continuous track circuiting of the Chesham branch, which allowed the existing electric train tablet installation to be taken out of use. At the time these were the only colour light signals in the Chalfont and Chesham areas (aside from the Chalfont up single line distant and a repeater for JV17 (RJV17) which were both installed at the same time).

When the Chalfont area was resignalled ten years later in 1959 JT25 & JT25 Co-Acting were removed and replaced by the current pair of signals (JW83 & JW83 Co-Acting) approximately 500-600 feet further from Chalfont. When control of the Chalfont area was transferred to Amersham Cabin in 1960 these two signals were renumbered to JT83 & JT83 Co-Acting.

In 1970, when Chesham signal cabin was closed, JV17 & JV17 Co-Acting were renumbered to JT69B & JT69B Co-Acting, and these signals were only removed when the track circuits on the Chesham branch were replaced by an Axle Counter in the early 1990s.

Would trainstops have been provided in this area from 1949? The 1959 notice mentions trainstops being fitted, but there's no mention in the 1949 one.

One wonders if the co-acting signals were simply a reassurance thing to make up for the lack of a tablet.
 

Jack Barry

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Indeed - I don't think anyone knows why it was done like that.

It may have been due to it marking the entry to a single line, so someone thought it was a good idea to put it there as an additional mitigation measure. However this isn't the full story, as other single lines didn't / don't have the same treatment. The only difference at Chalfont is that the signalling is in a multi-aspect layout, although again that doesn't really answer the question of why.

It may well remain one of life's mysteries!
Just back from a break and I see that this has been brought up elsewhere. I had a thought it was to do with steam locos and it seems to be correct if what has been said is true.
 

Jack Barry

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Co-actors are also used for signal-sighting issues, where it would be too difficult/expensive to move the original signal and wiring, a new co-acting signal is placed.
eg. Tower Hill, Whitechapel, Aldgate East, West Kensington.
Thanks for that although why they just don't commission the new signal and take out the old one.
 

edwin_m

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Thanks for that although why they just don't commission the new signal and take out the old one.
Usually when a co-actor is provided there is no single place for the signal that makes it adequately visible from all the places it needs to be. For example one may be visible from a distance and the other one close up.
 

Ken H

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is this sort of the same as in semaphore signalling where you have 2 arms on 1 post, one high up so it can be seen from a distance and low one for when close?
 

edwin_m

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is this sort of the same as in semaphore signalling where you have 2 arms on 1 post, one high up so it can be seen from a distance and low one for when close?
Yes. And some pointless waffle because I have to post 5 characters.
 

philthetube

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Thanks for that although why they just don't commission the new signal and take out the old one.
The co actor may be placed in front of the original signal and would require train stops and possibly the moving of block joints.
 
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