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Posted: Fri Nov 25, 2011 2:15 pm
by railwest
Therefore, the distant most certainly does not have to be set to danger before any associated stop signal can be set to danger.
Sorry, but that is quite wrong.
The physical nature of the mechanical (or electrical) locking between the lever working the distant signal and the lever(s) working the stop signal(s) in advance will be such that it is impossible to replace any of the stop signal levers UNTIL the distant lever has been replaced.
In later years, as the number of signals at some locations were reduced, it was not uncommon for a distant signal to become a colour-light worked as a 'repeater' from the same lever as the Home (in the same manner as Intermediate Block Signals). The aspect displayed by that C/L would be dependant upon the state of any stop signal in advanc eof the Home.
Posted: Fri Nov 25, 2011 10:39 pm
by jules
Sorry, but that is quite wrong.
Agreed and happy to clarify
I was talking "logically" rather than mechanically in the strict sense.
The effect of semaphore tappet locking is, of course, such that the home signal in the danger position locks the distant at caution, the desired effect. The home signal being operated frees the interlocking tappet to shift into the home signal blade notch, effectively unlocking the distant. When the distant signal then is cleared, its lever has a reciprocal action on the tappet, shifting it into the (necessary) notch on the home signal blade and locking it at clear, until the distant is replaced at caution.
As the rule book states a distant signal should be replaced at caution as soon as a train has passed it, this reciprocal locking should never be a problem. But a lapse signalman with an emergency on his hands who fails to replace the distant will *not be able* to set his home signal to danger until he has set the distant back to caution.
Not that there were many lapse signalmen around ...
Posted: Sat Feb 18, 2012 9:59 am
by Andrew
railwest wrote:In later years, as the number of signals at some locations were reduced, it was not uncommon for a distant signal to become a colour-light worked as a 'repeater' from the same lever as the Home (in the same manner as Intermediate Block Signals). The aspect displayed by that C/L would be dependant upon the state of any stop signal in advanc eof the Home.
This reminds me that there were 2 "Intermediate Blocks" on the Severn Beach line before singling. The first was at the Redland end of Montpelier platform. If I remember correctly, this did not have a Distant as it was, in effect an "Advanced-Advance Starter" for Stapleton Road. The next was at Sea Mills. the Distant was just outside the Clifton Down tunnel and the home was at the Shire end of Sea Mills platform. I don't actually recall any in the "down" direction at either location.....
Clifton Down's "down" Distant was a colour light in the tunnel.