I think it's generally the case with fire alarms, for fairly obvious
reasons (so they continue to work as long as possible even if a fire
is busy burning through their cables, even though these are armoured),
that they work on the basis of "if in doubt, sound", with things like
sirens often operating semi-independently of the control unit. So if
a surge triggers an alarm and the circuitary is then fried, it may be
quite difficult to get it all to stop other than by pulling the
breakers and waiting for the batteries in the sounders to run out,
which may be some time.

----------------------------------------------------

I had a similar problem at work a few years ago. The fire alarm started
wailing and the normal shut down didn't work.

Maintenance said they couldn't be there for over an hour. I had a show in
the theatre starting in less than an hour.

I brought out my trusty meter, saw it was a ground fault problem and, after
speaking with Fire Marshall who was on site answering the call, I cut the
green ground cable(s) of the effected alarms. Silence. :-)

As it was a ground fault and the other alarms in the building had shut down
when I turned the system "off" and were still working when I turned the
system back on, after cutting the ground wire in the effect alarms, so the
Fire Marshall allowed the show to go on.


--
Cheers
Roger Traviss


Photos of the late GER: -

http://www.greateasternrailway.com

For more photos not in the above album and kitbashes etc..:-
http://s94.photobucket.com/albums/l9...Great_Eastern/