"D7666" wrote in message
...
On Nov 30, 4:47 am, Charles Ellson wrote:

relays drop out causing an alarm;

reset up to three times in
succession before someone is sent

Nope. Respond at first alarm with an emergency fault. At least thats
how we do it on ''my'' bit of underground infrastructure.

--
Perhaps there is a risk that something happened, and people might be on or
around the tracks? You don't want to accidentally fry them.