Interlocking between distant and home signals?

You are here: Home > Forum > General > General questions, comments, and issues > Interlocking between distant and home signals?

Page 1 of 1

Interlocking between distant and home signals? 25/12/2011 at 12:43 #26151
maxand
Avatar
1637 posts 		On reading about distant and home signals, it appears there is often interlocking between them, so that the distant signal cannot clear unless home (and possibly starter) are also clear, giving the driver of an approaching train an indication that the line is clear as far as the home signal of the next signal box.

Now here we're talking signal boxes and semaphore signals, but the principles seem valid enough to be able to be applied to color light signals and remotely controlled signalling as in SimSig. Although when one looks at layouts one can clearly see distant and home signals applying to a particular station, I have never come across interlocking between them, though it shouldn't be any more difficult to program than, say, call-on.

Is this found in any sims?
Log in to reply
Re: Interlocking between distant and home signals? 25/12/2011 at 13:07 #26152
Late Turn
Avatar
696 posts
Online 		I think the best way of looking at it in a mechanically signalled area is that the distant signal requires all associated stop signals cleared first - slightly complicated by intermediate block signals (usually located in advance of the box) which have their own distant signal (the latter sometimes colocated with the section signal, often in the form of a three-aspect colour light). Sometimes you'll find a similar arrangement of signals (but not an IB section as such) in rear of the box, where the distant signal applies only to the home signal (for simplicity, a three aspect colour light), which in turn indicates the state of the remaining stop signals. Truro is a good example, I think; Elsham box (S Humbs) has this arrangement without semaphores (post resignalling only), and the GC developed the concept for widespread use (see Quorn box on the preserved GC for an example - see if you can work out what's going on and I'll knock a detailed explanation together if necessary).

Simsig exists (in its original form) to simulate multiple-aspect signalling on TCB lines, where things are simpler and a distant is only associated with the next stop signal (but might indicate the state of the second signal) - a representation of distants in semaphore areas features in Central Scotland and S Humbs though, I believe.

More later, perhaps - hope that (typed on my phone) makes sense in the meantime though!

Tom
Log in to reply
The following user said thank you: maxand
Re: Interlocking between distant and home signals? 25/12/2011 at 13:26 #26155
Zoe
Avatar
251 posts 		" said:
Now here we're talking signal boxes and semaphore signals, but the principles seem valid enough to be able to be applied to color light signals and remotely controlled signalling as in SimSig. Although when one looks at layouts one can clearly see distant and home signals applying to a particular station, I have never come across interlocking between them

A distant signal will only show green if all the associated stop signals have been cleared. In the case of many areas simulated by SimSig there is only one stop signal associated with the distant and this stop signal will only clear if the line is clear up to and including the overlap beyond the next stop signal.
Last edited: 25/12/2011 at 13:27 by Zoe
Log in to reply
The following user said thank you: maxand
Re: Interlocking between distant and home signals? 25/12/2011 at 15:17 #26160
DriverCurran
Avatar
683 posts 		You also need to bear in mind that with any form of multiple aspect signalling each signal is the distant for the following signal and the home/starter for the previous signal. Hence the terms distant, home, starter and advanced starter are no longer applicable

Paul
You have to get a red before you can get any other colour
Log in to reply
The following user said thank you: maxand
Re: Interlocking between distant and home signals? 25/12/2011 at 15:43 #26161
guyh
Avatar
54 posts 		Maxand,

If I understand your question correctly, then yes there are plenty of examples in SimSig.

I believe you have been playing with the Exeter sim, and there are examples there. At Athelney LC on the line from Westbury, the first pair of signals are 12R and 12. 12 is the equivalent of a semaphore section signal, and 12R is the equivalent of the distant signal in rear. 12 can only show red or green, and 12R is automatically interlocked to show the corresponding yellow or green.

In a semaphore arrangement the signaller would have to "replace" the distant signal to yellow / "on" first before replacing the section signal, but would obviously wait until he could be sure the train had passed the distant signal, so if a track circuit was available to show the train passed the distant, the signaller could then replace the signal, or the signaller might otherwise have to wait until he could physically see the train had passed the distant, for example when the train actually passed the signalbox.

In the modern colour light 2-aspect arrangement, there would usually be a separate track circuit beyond the distant / repeater which would automatically put the distant / repeater back to yellow.
Log in to reply
The following user said thank you: maxand
Re: Interlocking between distant and home signals? 25/12/2011 at 15:46 #26162
guyh
Avatar
54 posts 		...and maybe I should clarify further....
In SimSig the repeater or distant signal will not be controlled by the signaller, but will be controlled automatically in the interlocking, as it would be in an IECC or PSB equivalent; this is where the control of the signal itself is different to a manual-box area.
Log in to reply
Re: Interlocking between distant and home signals? 26/12/2011 at 04:27 #26178
maxand
Avatar
1637 posts 		Thanks for clarifying this issue for me.

Turning Panel Signals off helps by showing what aspects some of the automatic and repeater signals are showing (the ones that are functional here). Some repeaters at the edges of the sims don't show aspects at all, and may not even have a number, but maybe that's because they're being controlled by another box. E.g., the unnumbered repeater between 93 and W41 at Athelney. In some sims all the automatic signals have numbers, even if they don't all light up. No big deal.
Log in to reply
Re: Interlocking between distant and home signals? 26/12/2011 at 09:42 #26186
Firefly
Avatar
521 posts 		Quote:
Some repeaters at the edges of the sims don't show aspects at all
Because they're controlled by the adjacent box
Log in to reply
The following user said thank you: maxand
Re: Interlocking between distant and home signals? 26/12/2011 at 10:25 #26189
Peter Bennet
Avatar
5362 posts
Online 		" said:
Quote:
Some repeaters at the edges of the sims don't show aspects at all
Because they're controlled by the adjacent box
In SimSig terms they are "External automatics" - both main signals and related repeaters even if in reality they are manually operated signals. However In some Sims they are bespoke coded as "External manual" (for want of a better term) which means there is some code that sets the routes by reading the timetable:- the CSCOT entrance at Garnqueen Jn is a bespoke coded external manual system for example.

Peter
I identify as half man half biscuit - crumbs!
Log in to reply
The following user said thank you: maxand
Re: Interlocking between distant and home signals? 26/12/2011 at 20:39 #26207
kbarber
Avatar
1712 posts 		Another point is that a distant signal will usually have a separate switch/lever/route. In a lever frame the lever will be physically locked in the "Normal" (caution) position until all[1] the associated stop signals are cleared. Which signals those are is a matter of local knowledge - some boxes could have 4 or 5 whereas others might have only one. But if each of the stop signals is a 3 aspect colour light with full braking distance to the next stop signal, the lever is released by the next signal lever alone; following signal(s) will show Y or G according to the state of the next ahead throughout the control area. (I saw this at Biggleswade, where there was a distant & 3 stop signals on the Up Fast but they were placed at approximately even intervals so that, apart from the 2 aspect distant, they looked remarkably like 3-aspect mas (multiple aspect signalling - another for the wiki) to the driver, with the last in the sequence also acting as distant signal for Arlesy.

A repeater, on the other hand, doesn't normally have a separate control of any kind; it usually indicates just one stop signal and so may be allowed to work completely automatically. Common where there's 2 aspect signalling or when approaching a mas area (Biggleswade up distant could easily have been a repeater, for example, apart from requirements in the Rules & Regs to keep a distant a caution under certain circumstances).

[1] There were also places where boxes were very closely spaced and a distant might apply to signals worked by more than one box. Different companies devised different ways of dealing with this; I'm sure Danny252 will talk about the Western's (Block) Regulation 4A, for example.

An example I'm particularly interested in at the moment was on the main line from Lecester into St Pancras, before resignalling started to bring about changes in mid-1977.

South of Cricklewood the first box encountered was Watling Street Jc. 1110yd further on was West Hampstead at the north end of the station platform, with Finchley Road just 784 yards further south again. Speed on the Up (southbound) Fast was 80mph so braking distance was fairly substantial.

Finchley Road UF inner distant (No. FR24) was beneath West Hampstead starter at the south end of the platform; I don't suppose it was more than 650 or 700 yards to Finchley Road home. (Incidentally it was a co-acting set - there was a pair of high arms visible above the road bridge and a pair much lower down to be seen by a driver stopped close to the signal; a lovely beast.) Obviously the distant was "slotted" so it couldn't show clear while the stop arm above it showed danger. (In other words Finchley could pull his inner distant even while West Hampstead starter was normal; the point about a slot is that the control is applied at aspect level rather than interlocking level, in this case by a confection of weights & levers on the signal post.)

Finchley Rd UF outer distant (FR23) was, in turn, beneath West Hampstead home, which wasa a few yards in rear of WH box, so I guess a braking distance of 900 or so yards? Still not nearly enough. Slotted again (obviously) and also "backslotted" so that, if WH starter was at danger, the distant wouldn't clear when WH cleared his home. (I suspect backslotting is unknown to modern signalling so probably not worth adding to the wiki.)

West Hampstead UF inner distant (WH53) was beneath Watling Street starter, braking distance certainly less than 1000 yards & may have been nearer 900. So there was an outer distant beneath Watling Street home, which must have put it something like 1100 yards from WH home; interestingly this didn't have a separate lever but was worked from 53. This was considered far enough. (How's that for idiosyncracy, less than 1/2 mile apart?) Again there was the usual backslotting.

To give the necessary braking distance, WH53 was in fact also slotted by FR23, with the inner shown on FR diagram as R[sup]1[/sup]23 and the outer as R[sup]2[/sup]23. I suspect the reason for dual-controlling both was that 53 was motor worked & it was vastly easier to do it that way than to dual-slot R[sup]1[/sup]23 only. In this case, the slotting and (dual) backslotting were all performed electrically, much much easier than trying to keep a mechanical setup in any sort of adjustment.

Watling Street was abolished in summer 1977 and West Hampstead in spring '78, their areas taken over by Finchley Road. Finchley Road itself closed in April 1981, when the present West Hampstead PSB took over.
Log in to reply
Re: Interlocking between distant and home signals? 26/12/2011 at 20:46 #26210
Zoe
Avatar
251 posts 		The rule book defines a distant simply as a signal that can't display a stop aspect/indication, by this definition a repeater is a distant.
Last edited: 26/12/2011 at 20:54 by Zoe
Log in to reply
Re: Interlocking between distant and home signals? 26/12/2011 at 21:08 #26215
Danny252
Avatar
1461 posts 		Actually, unless higher braking distances were specified for that line speed, the standard is only 800 yards (1000 for falling gradient, 600 for rising). I can't say I've ever run across anything specifically referring to extending braking distances above a certain speed (though obviously this is why 4-aspect signalling eventually appeared).

4A has always seemed a bit odd. In essence, it's a special acceptance from box B (much like Reg 5) telling box A not to pull off his distants, as B's distants are not located far enough out to stop a train. However, in many cases, it's very likely that Box A is close enough to B's distants to be able to put in slotting between the distants, as with the MML example above. I can only assume that it was just cheaper to just have the signalmen do it, rather than put in all those extra slots!
Log in to reply
Re: Interlocking between distant and home signals? 26/12/2011 at 22:06 #26220
Danny252
Avatar
1461 posts 		" said:
The rule book defines a distant simply as a signal that can't display a stop aspect/indication, by this definition a repeater is a distant.
I was going to refute this, but my old rulebook doesn't have any mention of repeater signals, and my new one has pretty much the same text for distant and repeater signals ("stop at the next signal"). There's not even any mention of what distants at "clear" actually indicate!
Log in to reply
Re: Interlocking between distant and home signals? 26/12/2011 at 22:10 #26221
headshot119
Avatar
4869 posts 		" said:
" said:
The rule book defines a distant simply as a signal that can't display a stop aspect/indication, by this definition a repeater is a distant.
I was going to refute this, but my old rulebook doesn't have any mention of repeater signals, and my new one has pretty much the same text for distant and repeater signals ("stop at the next signal"). There's not even any mention of what distants at "clear" actually indicate!
Hasn't the rulebook recently removed the distinction between a repeater and a distant signal?
"Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer
Log in to reply
Re: Interlocking between distant and home signals? 26/12/2011 at 23:23 #26224
Danny252
Avatar
1461 posts 		" said:
" said:
" said:
The rule book defines a distant simply as a signal that can't display a stop aspect/indication, by this definition a repeater is a distant.
I was going to refute this, but my old rulebook doesn't have any mention of repeater signals, and my new one has pretty much the same text for distant and repeater signals ("stop at the next signal"). There's not even any mention of what distants at "clear" actually indicate!
Hasn't the rulebook recently removed the distinction between a repeater and a distant signal?
Working off the SVR Rulebook here. Oddly, it's the BR(WR)-based version which doesn't mention repeaters, whereas the more NR-style modern version explicitly mentions them.
Log in to reply
Re: Interlocking between distant and home signals? 27/12/2011 at 13:13 #26235
jc92
Avatar
3631 posts 		" said:
" said:
" said:
The rule book defines a distant simply as a signal that can't display a stop aspect/indication, by this definition a repeater is a distant.
I was going to refute this, but my old rulebook doesn't have any mention of repeater signals, and my new one has pretty much the same text for distant and repeater signals ("stop at the next signal"). There's not even any mention of what distants at "clear" actually indicate!
Hasn't the rulebook recently removed the distinction between a repeater and a distant signal?
they are now the same. some R prefixes remain due to the expense of replating every signal in the country (should now be a white triangle).

there is no such thing as a repeater anymore (banners excepted of course)
"We don't stop camborne wednesdays"
Log in to reply
Re: Interlocking between distant and home signals? 27/12/2011 at 13:51 #26243
Late Turn
Avatar
696 posts
Online 		The 'R' suffixes are surely going to remain where they already exist, irrespective of the change in terminology - a distant signal numbered '742R' is almost certainly going to precede the stop signal '742', so replating the distant signal would leave you with two signals with the same number!

Where distant signals are individually numbered (either because they're worked independently or, more recently, because that's what's tending to happen), there won't be an 'R' suffix anyway.
Log in to reply
Re: Interlocking between distant and home signals? 27/12/2011 at 14:00 #26246
Stephen Fulcher
Avatar
2027 posts
Online 		New schemes give repeaters a unique number in the numerical sequence with no "R" suffix.

A triangle at the top of the ID plate is used to signify a signal which is incapable of showing a stop aspect, and are used on signals with "R" suffixes as well as on new installations, and of course on older installations where distant signals are worked from an independent lever in a signalbox, and as such have their own unique number anyway.

As an example, when Coventry was resignalled, the signals at Kenilworth reading from Leamington are now LC6501 (which is a distant and incapable of showing a red, and as such has a triangle on its identification plate), followed by the first stop signal LC6503.

As Late Turn states below, there are at present no plans to remove any "R" suffix, as this would be disproportionately expensive and have no real gain.
Last edited: 27/12/2011 at 14:01 by Stephen Fulcher
Log in to reply
Back