Transition from semaphore to MAS (and vv)

[andrew jukes]

The context for this is the same as my question on distant signal locking - wanting to simulate the operation of signalling using a computer based interlocking, controlled with an IECC style computer screen. I need to know what the options are at the boundary between a traditionally signalled block section and a section signalled with multiple aspect colour light signals.

From Stanley Hall's useful little book 'BR Signalling Handbook', it sounds as though some limited use of colour lights (besides the common colour light distants) in semaphore areas has occurred, so it may be there are very few special issues. My uninformed approach would be:
- to start a colour light area either with a two aspect (green/yellow) colour light acting rather like a distant signal (the next signal being a 3- or 4-aspect colour light), or (if signal spacing is critical) to use a 3-aspect colour light as the starter at the end of the semaphore signalled block. In this case, once cleared (by the semaphore block's signalbox), the colour light would be backlocked by clearing the block's distant and the colour light signal's display of green or yellow would depend on the aspect of the 3- or 4-aspect signal in advance.
- to finish a colour light area with a three aspect signal with the green/yellow aspect worked as the distant signal of the semaphore signalled block in advance

No doubt displaying my ignorance again, but have I got it anything like right?

Andrew

[grovenor-2685]

This is very much one of those areas where every case is different, if looking at 'Modernisation Plan' vintage then the policy was generally to fit MAS to through routes so transitions were either temporary stageworks or were on branch lines. There were some guidelines issued as part of the BR signalling principles at that time, I'll look them out for you. Prior to the modernisation plan there must have been transitions for each of the big signalling schemes on the ECML, Newcastle, Thirsk, York? I don't know how they were done, could be some sort of clue in Nock's signalling book. I'll look at that as well.
On the LM we called these remaining mechanical boxes 'fringe boxes' on the main lines they were usually provided with a train describer linked to the main box and track circuit block, ie MAS, operated between the main box and the fringe with transition to block instruments on the other side of the fringe. emergency block bells were provided between fringe and main box for use if the train describer comms failed.
Branch line fringe boxes could work in the same way or could have manual block working to the main box depending on traffic levels.
This plan of Coventry has a number of examples, http://www.norgrove.me.uk/signalling/plans/Coventry.gif
Regards

[andrew jukes]

Thanks, Keith - very interesting. The splitting 4-aspect colour lights on the down fast at Coventry were a surprise.

In terms of my question, the Leamington line looks to offer most. At Gibbet Hill, it looks like lever 30 works as an up distant and lever 4 (if I could be sure of the symbols!) is the Gibbet Hill down starter, followed by colour light 'distant' R4 (I'm assuming the black circle is a blanked out aspect) offering Y/YY/G.

I'll be interested to see what you turn up both on the BR principles and on the earlier schemes. I have a suspicion that, provided what I do makes sense in signalling terms, there will be lots of choice in the detail.

Regards

Andrew

[grovenor-2685]

I found the relevant info in the old BR standards and have attached the relevant extract here.

Principle-22.pdf

(15.66 KiB) Downloaded 235 times

(Should be OK now!)

App-D.gif

(389.01 KiB) Downloaded 251 times

Regards

[andrew jukes]

Thanks, Keith - that's perfect.

In terms of a model representation, it seems to me the three methods are logically identical and not that different from normal co-located starter and distant signals. The important point is that the indications at each of the transition signal positions are controlled from two separate sources, with the stop signal being controlled by the mechanically signalled block's signalbox and the 'distant' indications being controlled by the signal in advance, either the 3-aspect colour light or (where starter and home are both involved) by the starter. Differences from normal mechanical distants are that the control is automatic (though slotted with the stop indications) and, because the control is automatic, no backlocking of the 3-aspect colour light in advance is needed. Hope that's a correct summary - if so, it shouldn't be too difficult to arrange the interlocking and inputs to achieve that on the screen though providing outputs to achieve Method 2 on an actual model could be fun!

One question on the diagram - what exactly is the distant symbol under the home on 1(b) meant to signify?

Is there by any chance similar information in the old BR standards for the transition the other way - MAS to semaphore?

Thanks again

Regards

Andrew

[grovenor-2685]

Is there by any chance similar information in the old BR standards for the transition the other way - MAS to semaphore?

Wondering why you asked this, as it is included in the standard, I discovered that the pdf file I so laboriously made somehow came out to be blank. Surprised you didn't comment, the appendix makes more sense if looked at when reading the text. I have now replaced the pdf with a tried and tested one.

One question on the diagram - what exactly is the distant symbol under the home on 1(b) meant to signify?

It is just to show that the distant arm is slotted by the starter ahead so it can only clear if the home and starter are both clear.
Regards

[andrew jukes]

I should have been more curious about the blank pdf. I just assumed it was an alternative way of sending appendix D. (but why would you do that?!).

The text seems to answer all the questions, so thanks for the laboriously made pdf. It seems I was partly right on the colour light to semaphore transition, at least.

Regards

Andrew

[beast66606]

Late arriving to this thread.

to start a colour light area either with a two aspect (green/yellow) colour light acting rather like a distant signal (the next signal being a 3- or 4-aspect colour light),

the next signal could be a 2 aspect R/G

or (if signal spacing is critical) to use a 3-aspect colour light as the starter at the end of the semaphore signalled block. In this case, once cleared (by the semaphore block's signalbox), the colour light would be backlocked by clearing the block's distant and the colour light signal's display of green or yellow would depend on the aspect of the 3- or 4-aspect signal in advance.

Again the signal in advance could be a simple 2-aspect

to finish a colour light area with a three aspect signal with the green/yellow aspect worked as the distant signal of the semaphore signalled block in advance

There is no reason why the end of a colour light area could not be a 2-aspect R/G signal with the next signal being either a colour light or semaphore distant, in fact there are a couple of examples of panel boxes working semaphores which were motor worked as "starters", a small panel box locally to me worked a semaphore starter for a few years until it was replaced with a R/G colour light.

hth

[grovenor-2685]

Indeed those are possible situations, but the question concerned transition from semaphore to MAS where 2 aspect red/greens are not the norm.
Cheers

[grovenor-2685]

Indeed those are possible situations, but the question concerned transition from semaphore to MAS where 2 aspect red/greens are not the norm.
Cheers

[beast66606]

Indeed those are possible situations, but the question concerned transition from semaphore to MAS where 2 aspect red/greens are not the norm.
Cheers

Really - or the ones you know of ? - Chester PSB has 2-aspect on "my" line, MAS = multiple aspect and 2 is multiple ... so my comments are perfectly valid - it only confuses those who don't know if we quote inaccurate information.

[grovenor-2685]

A particular example is not the norm! (and I agree that the published BR standard would not neccessarily be the norm either, as any new standard is only gradually applied and as it becomes widespread gets superceded by a new one and dwindles again). Certainly by the definitions used in the steam/diesel transition period 2 aspect was not considered to be MAS, multiple meant more than 2. And with many miles of high density mainlines crying out for resignalling no-one was wasting money resignalling lines where the traffic density would allow use of 2 aspect signalling, they were a long way down the queue.
And everything I quoted I gave sources for, it was not 'inaccurate'.
I rather suspect, beast, that your memory of the early 1960s is not quite the same as mine, I was working in the LM region signalling modernisation team, where were you?
These days things are different and I will happily concede you have a deeper knowledge of the current scene.
Best regards

[beast66606]

Meant to answer this a bit quicker !

The context for this is the same as my question on distant signal locking - wanting to simulate the operation of signalling using a computer based interlocking, controlled with an IECC style computer screen.

How many IECCs did you get involved with Keith

I rather suspect, beast, that your memory of the early 1960s is not quite the same as mine, I was working in the LM region signalling modernisation team, where were you?
These days things are different and I will happily concede you have a deeper knowledge of the current scene.

If we take this at face value then it means research is pointless - I mean it's not like I own the G or subsequent notices, study power box schemes, new and old and there appears to be little point if I did.

And of course the OP didn't mention a date ...