(22-10-2010, 02:07 PM)Peter Wrote: PJW, you say about a route being normal when the signaller has cancelled the route and the signal is at red and proved at red, but in pure terms, would you not expect all approach locking and route holding to have timed out (you certainly would not set route A which required route B normal until this is so).
I guess historically it all comes from the position of the lever controlling that signal. If the lever is normal then it would directly relate to an "aspect".
Indeed- that is why I listed a) AND b) AND c), with c being the Approach Locking of which you speak. [I note that I missed writing explicitly the second word AND and have now added intoo that post]
In terms of a mechanical signal operted by a lever frame, if the locking of signals against points is entirely mechanical, then the lever (to current although not historic standards) would be fitted with a "back lock" to prevent it being placed completely NORMAL in the frame- it will be able to be returned sufficiently that the signal arm is horizontal (and thus the signal displaying danger) but until it has been established that the signal has been back at danger long enough then the electric lock won't energise- the signal lever will be sufficiently "out" that the points will still be locked by it. This I think is the origin of "route normal"; a colour light signal replacing a bracket semaphore signal would retain a separate lever for each of the various routes, that used to drive individual arms / indicators on the signal post.
Route Normal does not include the asociated route locking; part of the route locking may still be locked by an occupied track in the route, but yes the route is unset and the approach locking is free.
PJW