(09-09-2010, 08:47 PM)Alasdair Wrote: Thanks Peter,
Excellent advice, and I had spent ages trying to figure out what ARAFOAL stood for - now I know.
Alasdair
Mainly a Britih Rail "Western Region" term
At Red And Free Of Approach Locking
though in SSI data it is just
foal = free of approach locking
but actually means exactly the same as approach locking does require the signal to be proved controlled to red (i.e. aspect relays requiroing a red, but not necessarily proved alight). The thing is in RRI the relay itself must be down proved to make sure it has responded correctly whereas wheter SSI drives a lamp electronically (i.e. not interfaced via a relay) then there is no such need as computers don't fail like that- if there is a fault then it is detected and the TFM shuts down its output interface- which means that a red is illuminated by a diverse path anyway and so therefore it is not an issue
PJW