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CD/RA and OFF indicators

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Re: CD/RA and OFF indicators

Unread postby Mike Hodgson » Fri Sep 9, 2016 10:02 pm

According to the Railsigns site, the original OFF indicators were Southern Railway (as early as 1928) with a corresponding ON indication, which became obsolescent during WW2. I can't see how it would be acceptable for those versions of the indicator to do other than follow the signal aspect directly.
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Re: CD/RA and OFF indicators

Unread postby StevieG » Fri Sep 9, 2016 10:19 pm

Mike Hodgson wrote:According to the Railsigns site, the original OFF indicators were Southern Railway (as early as 1928) with a corresponding ON indication, which became obsolescent during WW2. I can't see how it would be acceptable for those versions of the indicator to do other than follow the signal aspect directly.
I'd agree Mike.
And 1950s (& later?) photos have shown that the '1949' signalling at Liverpool Street also operated stencil ON as well as OFF platform indicators.
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Re: CD/RA and OFF indicators

Unread postby davidwoodcock » Sat Sep 10, 2016 8:40 am

Mike Hodgson wrote:According to the Railsigns site, the original OFF indicators were Southern Railway (as early as 1928) with a corresponding ON indication, which became obsolescent during WW2. I can't see how it would be acceptable for those versions of the indicator to do other than follow the signal aspect directly.


Brighton station, when resignalled with colour lights in 1932, had what were described on the diagram as intermediate platform signals which could display red (bottom), yellow or green full-size aspects together with an indicator at their side which displayed "M" or "S" according to whether a main or shunt indication was being repeated. I don't know whether the signals concerned displayed any form of identification plate but they certainly weren't separately numbered.

The relevant instruction read:
Intermediate Platform Signals at Terminal. These signals will work in conjunction with the platform road starting signal, also with the shunt signal controlling movements from the platform road concerned. The indicator at the side of the signals will display the letter “M” or “S” to denote whether the movement is to be made under the authority of the main starting signal, or the shunt signal, respectively.”
In addition, trains or locos standing completely within (i.e. the buffer stop side of) the Intermediate Platform Signals weren't permitted to pass them when a red aspect was displayed.

I have found a couple of photographs which show that the IP signals at Brighton were still extant (and presumably operational) in 1965.

Intermediate Platform Signals had also been provided during resignalling at Charing Cross (1926) and London Bridge (certain terminal platforms only, 1929), and presumably also at Cannon Street (1926). I lack information on whether they were provided in the earlier schemes at Blackfriars and/or Holborn Viaduct.

When Waterloo was resignalled in 1936 "ON" and "OFF" indicators and TRTS plungers were provided for the information of platform staff - so the "ON" indicator could obviously be passed by trains/locos provided that they did obey the platform end signals.
Last edited by davidwoodcock on Sat Sep 10, 2016 10:32 pm, edited 3 times in total.
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Re: CD/RA and OFF indicators

Unread postby kbarber » Sat Sep 10, 2016 4:27 pm

John Hinson wrote:
kbarber wrote:TRTS plungers are likely anywhere that trains are likely to spend a significant amount of time at a platform, I'd have said.

. . . but not at a London terminus where both you and I worked, nor at another London terminus I worked at.

John

True, which could be a bit of a pain in the peak. But IIRC the time-off was only 30 seconds so the frustration was kept within bearable limits.
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Re: CD/RA and OFF indicators

Unread postby Mark Lamb » Sun Sep 11, 2016 10:10 am

Signal-sighter wrote:Back facing indications are amber, not yellow (a classic interview question is "where is the colour amber used in railway signalling?"). Contrary to an earlier post an RA indication supplements and OFF indication - it will not cause an illuminated OFF indication to extinguish.


On Manchester Piccadilly station platforms there are single fibre-optic indicators that can show two displays. The OFF indicator is extinguished when the RA is given (actually, just R). This saves having two indicators; I can't see the point in having an OFF indicator still illuminated when the the RA is displayed.


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Re: CD/RA and OFF indicators

Unread postby JRB » Sun Sep 11, 2016 10:40 am

If the signal was put back after RA had been given, It could just be useful for the driver to see the OFF cancelled.
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Re: CD/RA and OFF indicators

Unread postby Mike Hodgson » Sun Sep 11, 2016 1:02 pm

JRB wrote:If the signal was put back after RA had been given, It could just be useful for the driver to see the OFF cancelled.


Perhaps but I thought this was supposed to be for the benefit of station staff rather than drivers. I agree it would help if station staff refrain from blowing whistles/waving flags to egg the driver on in this situation. If you are not using the old stencil type but a LED matrix type display capable of displaying OFF and R, the control circuitry could just as easily be designed to display ON just like the original SR version - but I question whether it is reasonable to expect the station staff to notice, as this event is not part of their routine and they may well not know why the signal was restored. I think this is where we rely on the driver to notice the big red light, TPWS if applicable and presumably the signal also has to time out before any conflicting movement can be signalled.
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Re: CD/RA and OFF indicators

Unread postby Fast Line Floyd » Sun Sep 11, 2016 6:28 pm

Mike Hodgson wrote:
JRB wrote:If the signal was put back after RA had been given, It could just be useful for the driver to see the OFF cancelled.


Perhaps but I thought this was supposed to be for the benefit of station staff rather than drivers. I agree it would help if station staff refrain from blowing whistles/waving flags to egg the driver on in this situation. If you are not using the old stencil type but a LED matrix type display capable of displaying OFF and R, the control circuitry could just as easily be designed to display ON just like the original SR version - but I question whether it is reasonable to expect the station staff to notice, as this event is not part of their routine and they may well not know why the signal was restored. I think this is where we rely on the driver to notice the big red light, TPWS if applicable and presumably the signal also has to time out before any conflicting movement can be signalled.

OFF indicators are just for train dispatch staff, where as the CD/RA is just for the driver.
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Re: CD/RA and OFF indicators

Unread postby John Webb » Thu Sep 15, 2016 9:36 pm

I'm going to illustrate the work I'm now doing on these indicators in this thread rather than in the main Works 2016 thread for St Albans South.
The 'OFF' indicator running on the original 55W car headlamp bulb:
Image

Rear view of the unit and interior:
Image
Note the neatly tied-up fibre optics.

Close-up of the lamp unit:
Image
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Re: CD/RA and OFF indicators

Unread postby John Webb » Thu Sep 15, 2016 10:15 pm

A close-up of the partly dismantled lamphouse:
Image

The reflector on the right is glass - in shape and size very similar to the 12v GU 5.3 reflector bulbs. With a bit more dismantling it was possible to try out a 3.5W LED bulb, similar to those we've used in some of our other signals:
Image

Rather less bright - a 5w bulb might be a little better. I'm thinking about incorporating these indicators into a revision of our 1970s colour light signals - minor but persistent problems with these needs some attention.
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Re: CD/RA and OFF indicators

Unread postby John Webb » Fri Sep 16, 2016 10:05 am

We've been told by the donor that these indicators came from Edinburgh, for information.
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Re: CD/RA and OFF indicators

Unread postby John Hinson » Fri Sep 16, 2016 10:16 am

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Re: CD/RA and OFF indicators

Unread postby Fast Line Floyd » Fri Sep 16, 2016 11:45 am

John Hinson wrote:Not Stockport, then:
http://www.geograph.org.uk/photo/3147697

John

I have a photo of the old WH5 platform starter at St Pancras just before the station remodelling started, this too had a same display, the driver of the HST that was in the platform waiting to depart whilst I took the picture had no idea why I was taking such a photo - until I told him!
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Re: CD/RA and OFF indicators

Unread postby Signal-sighter » Fri Sep 16, 2016 3:53 pm

Fast Line Floyd wrote:OFF indicators are just for train dispatch staff, where as the CD/RA is just for the driver.

There are numerous locations in Scotland where local instructions permit a driver to take an illuminated OFF indication as a movement authority.
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Re: CD/RA and OFF indicators

Unread postby Fast Line Floyd » Fri Sep 16, 2016 8:09 pm

Signal-sighter wrote:
Fast Line Floyd wrote:OFF indicators are just for train dispatch staff, where as the CD/RA is just for the driver.

There are numerous locations in Scotland where local instructions permit a driver to take an illuminated OFF indication as a movement authority.

That may be so but that is not what they are designed for and in most cases either a signal should be provided for the move even if it repeats another signal or a banner repeater should be used.
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