Aspect Step Pattern with LU MAS

[Deleted]

I was watching A968 (Chorleywood n/b starter) yesterday and noted how it cleared to yellow in the correct way, i.e. the yellow aspect came on, the trainstop dropped and eventually the red was extinguished. Later I watched as it switched to green, with no wait.

Compare this to JB3, the platform 1 n/b starter at H-o-t-H. When this one was cleared, it cleared to yellow, and then rapidly stepped up to green!

What does the aspect step circuit look like on these signals? I always figured that the four-aspect controlled signals could clear directly to any of the three 'off' aspects.

[Harsig]

TheOneKEA said:

I was watching A968 (Chorleywood n/b starter) yesterday and noted how it cleared to yellow in the correct way, i.e. the yellow aspect came on, the trainstop dropped and eventually the red was extinguished. Later I watched as it switched to green, with no wait.

Compare this to JB3, the platform 1 n/b starter at H-o-t-H. When this one was cleared, it cleared to yellow, and then rapidly stepped up to green!

What does the aspect step circuit look like on these signals?

Here is the relevant section of circuitry for JB3

JB3 Wiring (75KB)

I always figured that the four-aspect controlled signals could clear directly to any of the three 'off' aspects.

They can. It depends on circumstances. In the case of A968 since it is an automatic, it will generally only be at danger due to the presence of a train and so when it clears, the train has moved into the next section, protected by the next signal A970 being at Danger. Thus A968 will always clear to single yellow and then later to green when the train has passed clear of the next section. The delay associated with the change from red to yellow is associated, as you've guessed, with the trainstop on A968. When A970 clears from red to yellow A968 will continue to show only yellow while the trainstop on A970 is lowering and will only change to green when both A970 is clear and A970's trainstop is proved fully lowered. Thus there is no delay visible on the signal A968 for the change from yellow to green.

In the case of JB3 it is a controlled signal, it can clear to any aspect dependent on the state of the signals ahead. Since the next signal JB7 is also a controlled signal this produces the effect you witnessed. Under normal circumstances the signalman will clear JB3 and JB7 at the same time. However although JB7 may be clearing straight to green, because JB7's trainstop has not yet lowered JB3 will initially clear only to yellow but will step straight up to green once JB7's trainstop is fully lowered (provided of course that JB7 is showing at least double yellow)

[Tom]

Now that is PROPER circuitry (even if the symbols do look a bit alien to me). ;D

[Deleted]

Ah, once again you deliver Harsig. Thanks

[Deleted]

TheOneKEA said:

Ah, once again you deliver Harsig. Thanks

If you have got JB7 showing a green aspect, and then you clear JB3, it will not go straight to Green, but step up through the series, like with any M.A.S or a stop signal that has a repeater on the same post.

[Harsig]

Met said:

If you have got JB7 showing a green aspect, and then you clear JB3, it will not go straight to Green, but step up through the series, like with any M.A.S or a stop signal that has a repeater on the same post.

I don't think so. Have you actually tried that on the simulator?

[Tom]

I would agree with Harsig - assuming 3DR is up the signal should step to green immediately.

And we've already established elsewhere that repeaters on the same post can step straight to green.

[Deleted]

Harsig said:

I don't think so. Have you actually tried that on the simulator?

Nope i have tried it at Harrow!! The same applies for the southbound route towards Marylebone.

[Harsig]

Tom said:

I would agree with Harsig - assuming 3DR is up the signal should step to green immediately.

Exactly. The conditions for 3DR up is

852V off & 852HR up & 7V off & 7HR up

all of which are guaranteed if JB7 is showing a green aspect.

[Deleted]

Harsig said:

The conditions for 3DR up is

852V off & 852HR up & 7V off & 7HR up

I dont understand any of that as believe it or not, operational OPT doesnt include such deep level knowledge! Iam not a signalling anorak!

Harsig said:

all of which are guaranteed if JB7 is showing a green aspect.

I do remember doing what i said at Harrow with them just to see what would happen.

[Tom]

Met said:

I dont understand any of that as believe it or not, operational OPT doesnt include such deep level knowledge! Iam not a signalling anorak!

This is great; we can look informed and intelligent (I hope TheOneKEA is reading up on his signalling alphabet so he can join in) ;D

It translates as: A852 trainstop down and A852 yellow and JB7 trainstop down and JB7 yellow.

The only time I can think of it not stepping up immediately is if A852 has just cleared and its trainstop is a little slow. Perhaps if the trainstop and valve were changed the conditions you experienced would not occur.

[Harsig]

Tom said:

The only time I can think of it not stepping up immediately is if A852 has just cleared and its trainstop is a little slow.

Ah but that means that JB7 would not be showing a green aspect either.

[Tom]

But surely JB7 only needs to be showing one yellow to pick 3DR?

And someone remind me (as I haven't worked Harrow cabin for a few years) do the diagram indications show the yellows or just an off/on aspect?

[Harsig]

Tom said:

But surely JB7 only needs to be showing one yellow to pick 3DR?

And someone remind me (as I haven't worked Harrow cabin for a few years) do the diagram indications show the yellows or just an off/on aspect?

The original premise from Met Apprentice was if JB7 was green then JB3 would still step up through the aspects.

In fact while 3DR up only requires 7HR up, 7HHR will also be up as it is fed over the same contacts on 852V and 852HR as 3DR.

The diagram in Harrow Cabin shows only On/Off indications for the signals.

[Tom]

I'm probably getting a bit lost in my own head here (I'm going to be sitting in the SSL design office in a few weeks tearing my hair out), but let's assume A852 has just cleared, but the trainstop is still lowering at the same time that JB3 clears.

The state of the signalling will be:
852HR up, 852V on, 7HR up, 7HHR down, 7V off, 3DR down, 3HHR up. JB3 would therefore momentarily step to double yellow then green when 852V finally goes to the off position.

Assuming that A852 is already clear when JB3 clears we get:
852HR up, 852V off, 7HR up, 7HHR up, 7V off, 3DR up, 3HHR (don't care), and JB3 would clear from red straight to green.

It would appear then that the debate is based on the position of the previous train, and I can't quite see how Met Apprentice's statement about JB7 being green comes into the equation, as it appears that JB7 can either be double yellow or green for JB3 to step straight from green.

Perhaps he was going by the diagram KE's alone when making the statement about JB7, I don't know if it can be seen from the cabin or not.

Unless of course I'm missing something else...?

[Deleted]

WHEEEEE!!!!!!

I love it when I start a good thread!

Although I will admit that I don't know a single letter of the signalling alphabet; perhaps someone knows if it has been published anywhere? ;D

[Tom]

TheOneKEA said:

WHEEEEE!!!!!!

I love it when I start a good thread!

Although I will admit that I don't know a single letter of the signalling alphabet; perhaps someone knows if it has been published anywhere? ;D

Harsig posted a link to the old Railtrack symbols/ alphabet standard a few weeks ago elsewhere, I'll try and dig a copy out in the meantime.

[Deleted]

Thanks BAET.

Now for the fun part - what does the aspect step pattern circuit look like for the link between A860 and A864, and the same between JP1 and JP2? How is the logic handled for the transition from 3 to 4 aspect and 4 to 3 aspect?

[Harsig]

TheOneKEA said:

Thanks BAET.

Now for the fun part - what does the aspect step pattern circuit look like for the link between A860 and A864, and the same between JP1 and JP2? How is the logic handled for the transition from 3 to 4 aspect and 4 to 3 aspect?

Basically the aspect of the signal is displayed is controlled by two or three realys depending on whether it is three or four aspect. These relays are called

HR
HHR (Four aspect signals only)
DR

Simply put in the case of a four aspect signal the state of the HR determines whether or not the signal is showing a proceed aspect. The HHR determines whether or not the signal should be showing Double Yellow or better and the DR determines whether or not the signal should be showing a green aspect. To summarise:

HR de-energised: Signal Red
Only HR energised: Signal Single Yellow
HR & HHR energised, DR de-energised: Signal Double Yellow
All three realys energised: Signal Green

In general the conditions for each relay to become energised are

HR: Section clear up to and including overlap beyond next signal
HHR: next Signal in advance showing a proceed aspect
DR: next TWO signals in advance showing proceed aspects.

For a three aspect signal the HHR relay is ommitted although in fact really it is the DR that is ommitted and the HHR is renamed the DR
To summarise (three aspect):

HR de-energised: Signal Red
Only HR energised: Signal Single Yellow
HR & DR energised: Signal Green

In general the conditions for each relay to become energised are

HR: Section clear up to and including overlap beyond next signal
DR: next Signal in advance showing a proceed aspect

Most often each signal will have its own set of relays but sometimes the HHR and DR can be shared between several signals although each signal will always have its own HR. An example of a shared relay can be seen on the link I posted near the beginning of this thread and better still it links a three aspect signal with a four aspect signal.
The signals concerned are JB3, the northbound starter from platform 1 at Harrow on the Hill (four aspect) and JB93, the northbound starter from platform 2 at Harrow (three aspect) Only one of these signals can be cleared at any one time and both read up to the same signal in advance JB7. Each signal has its own HR (3HR & 93HR) but the next relay in the sequence (the one which proves JB7 is clear) is shared by then both and is numbered 3HHR/93DR and this neatly shows how the HHR of a four aspect signal carries out the same function as the DR of a three aspect signal. JB3 also has the third relay 3DR but this is not shared with JB93 because the latter is only a three aspect signal.

[Harsig]

Tom said:

Harsig posted a link to the old Railtrack symbols/ alphabet standard a few weeks ago elsewhere, I'll try and dig a copy out in the meantime.

Here it is again

In fact if you want to know what all these letters mean, or might mean, then look at Appendix D (page 16) of the following document

www.rgsonline.co.uk/docushare/dsweb/Get/Rail-6314/rt0205_1.pdf
(Warning: The file is nearly 1MB)

[Tom]

Slightly offtopic I know, but I fell asleep this morning and ended up at Gunnersbury, the EB starter there stepped straight from red to green when my district train back to civilisation was due.

[Deleted]

Tom said:

Slightly offtopic I know, but I fell asleep this morning and ended up at Gunnersbury, the EB starter there stepped straight from red to green when my district train back to civilisation was due.

Quite normal for that particular signal.

[Tom]

I thought as much, so there must be similar scenario on LU as I doubt the signal selection circuitry differs that much.

[solidbond]

But remember, that signal, GB8 will NOT display a yellow aspect when the route is set for Turnham Green, as the next signal is the first one controlled by Earl's Court.

[Deleted]

solidbond said:

But remember, that signal, GB8 will NOT display a yellow aspect when the route is set for Turnham Green, as the next signal is the first one controlled by Earl's Court.

Really? I always thought that GB8 was 'slotted' by WK1, and that if WK1 was at red, GB8 could only clear to single yellow if the diverging route was set.

[Tom]

That surprises me too, from knowledge of my own BR boundary I'm pretty sure that WS8 can clear to a single yellow with route indicator onto the LU section.

[DWS]

TheOneKEA said:

Really? I always thought that GB8 was 'slotted' by WK1, and that if WK1 was at red, GB8 could only clear to single yellow if the diverging route was set.

There has never been any slotting between BR/Network Rail or LT/LUL in the Gunnersbury / Turnham Green area

[Deleted]

DWS said:

There has never been any slotting between BR/Network Rail or LT/LUL in the Gunnersbury / Turnham Green area

So what's the proper term then?

[solidbond]

Tom said:

That surprises me too, from knowledge of my own BR boundary I'm pretty sure that WS8 can clear to a single yellow with route indicator onto the LU section.

ahh - but we are talking about GB8
I can assure you, GB8 NEVER shows a yellow aspect when set for the District, as normally, WK1 only clears as a train approaches the repeater, therefore it would be rare for GB8 to ever show a green aspect, if it was 'repeating' WK1

[Deleted]

Ah, now it makes sense ;D

But why is WK1 cleared in that fashion?