I agree with what the other Peter wrote initially, but would clarify (as per your diagam) that the Replacement control button is offset to the track on the control panel rather than being in line with it.
I don't actually know answer to your specific case- I am not familiar with the MCB with Obstacle Detectors (don't have any on the Underground!). I guess though that the clue is that the overlap extends across the crossing so perhaps there is some locking imposed by that outer signal; i.e. it may be plated as an Auto signal to denote it is passable by driver's authority, but from a signal engineering locking perspective it may be treated as a controlled signal.
However I am a bit confused because
a) never used to regard a level crossing in the overlap as something which should be ocked (unless very close), and
b) I thought that NR had decided to plate all signals as non-passable nowadays, regardless of whether they are auto signals from a signalling engineeering perspective.
Hence very keen to earn the correct answer from someone more up to date with mainline practice than I currently am.
I don't actually know answer to your specific case- I am not familiar with the MCB with Obstacle Detectors (don't have any on the Underground!). I guess though that the clue is that the overlap extends across the crossing so perhaps there is some locking imposed by that outer signal; i.e. it may be plated as an Auto signal to denote it is passable by driver's authority, but from a signal engineering locking perspective it may be treated as a controlled signal.
However I am a bit confused because
a) never used to regard a level crossing in the overlap as something which should be ocked (unless very close), and
b) I thought that NR had decided to plate all signals as non-passable nowadays, regardless of whether they are auto signals from a signalling engineeering perspective.
Hence very keen to earn the correct answer from someone more up to date with mainline practice than I currently am.
(20-05-2013, 11:44 AM)nionita Wrote: Hi Peter,
Thank you very much for your prompt answer.
I have a special situation (please see the attachment) where before the level crossing protecting signal is an automatic signal with replacement button facility.
I understand an automatic signal can be an exit from a controlled signal but why it is still require an entrance button if it has a separate replacement button?
Thanks again.
Adobe
PJW