Signal Time Out

No points in advance of that signal are in the overlap at all and can be moved at any time with a train approaching the signal. If the calling-on were to come off I see no reason why any of them should become locked for 240 or even 120 seconds.

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Surely it should be the route class for the approaching train, not for the route set for the signal, that matters. I can see Izzy's point that if a train is approaching a red at main-line speeds and braking, you want the full 120 seconds even if it's a calling-on route that's been pulled. But equally, if the train is coming out of a siding on two whites, 30 seconds should be enough even if it's a main route that's been pulled.

Yes, but the route class in rear is lost as the train enters that route, the entry route "class relay" (MER, SER, MER(C), (M,S,W or C) NLR, amnogst others depending on interlocking type (not exhaustive) ) begins to release that route behind the train as soon as it replaces the entry signal. So, the signal that you pull the button on in many cases has no way of knowing what class route was set up to it. Hence we use the longest, worst case, timer length.

but this is all extra work for little benefit

It seems the world moves on as we get older - so some things have changed, thanks for the examples Geoff - especially that one at Basingstoke. I'm so glad i don't need to keep on top of it anymore since i retired.

Kbarber - i'm not sure of when the Kent Coast phase 2 was actually commissioned, but that is the incarnation of Margate that i was talking about - my guess is mid to late 1950's. Basically it was one of two boxes relocked to signal the whole Margate area utilizing the existing lever frame in Margate "A" box- replacing all the mechanical equipment with colour light signals and electric point machines. Most boxes treated like this had some sort of route release timers - but for some reason i don't know, Margate didn't have them.

The Brighton mini-lever frames were actually a generation older than the Kent Coast Phase 2 Margate, so possibly had even more diffeent ways of working. One thing i am certain of though....many signalmen were familiar with how to help themselves to a release on the K and L type frames (many have told me stories of this). You just had to know where to stick your fingers in...

I know who has the Battersea Park frame and he has a pretty encyclopaedic knowledge of working and interlocking of those frames; I must ask him what the situation was when it was in service there.

I know who has the Battersea Park frame and he has a pretty encyclopaedic knowledge of working and interlocking of those frames; I must ask him what the situation was when it was in service there.

Apparently in later years a number of frames (including two power frames) were fitted with time-outs, but in each case the timer had to be initiated by pushing a button after returning the signal lever to the backlocked (B lock, for the technical) position.

kbarber in post 154688 said:

Apparently in later years a number of frames (including two power frames) were fitted with time-outs, but in each case the timer had to be initiated by pushing a button after returning the signal lever to the backlocked (B lock, for the technical) position.

What's the backlocked position?

kbarber in post 154688 said:

Apparently in later years a number of frames (including two power frames) were fitted with time-outs, but in each case the timer had to be initiated by pushing a button after returning the signal lever to the backlocked (B lock, for the technical) position.

What's the backlocked position?

Apparently approach locking that didn't time out was a Southern standard, both for power frames and for mechanical frames working colour light signals. My contact referenced an unofficial tool used to release the backlock at a certain (rather busy) mechanical frame, but otherwise the S&T needed to be called to release you. Apparently in later years a number of frames (including two power frames) were fitted with time-outs, but in each case the timer had to be initiated by pushing a button after returning the signal lever to the backlocked (B lock, for the technical) position. There were also a few boxes where an NX panel was installed alongside the L frame that acquired automatic timeouts when the panel was installed.

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The South Croydon frame (now Everglades at Gt Cockcrow Rly) definitely didn't times out as Neil Brady would confirm, as you say was Southern 'thing' to save a few coppers maybe?

Another question on the topic of approach locking / route timeouts...

On Crewe simulation, I had the following situation:
Signal WD161 on DF right before Acton Bridge (I put a reminder on it) has failed on Y/YY aspects (R/G still working).
On the attached savegame, 4S44 is approaching.
When setting the route from WD161 to WD163, WD161 gets unlit, therefore WD159 reverts to danger and 4S44 gets an ACOA.
After that, when cancelling the route from WD161 to WD163 again, it gets cancelled immediately.

Shouldn't there be approach locking in that case? Or is the fact, that WD159 had been reverted to danger, really enough for it not to be necessary?

Stephan