On May 10, 1:47*pm, "Dave Liquorice"
wrote:
Are there any mains powered (battery backed), linked smoke detectors
that have an "aux ouput" that could be used to release a magnetic
catch on a fire door?

Could the link be hijacked? Is there enough power available to
operate a small relay that could drop the supply to the magnetic
catch?

--
Cheers
Dave.

If you have a centrally conrolled fire alarm system (ie with a control
panel), they all have this feature. (Via a relay). It is the same
circuit that sets off the bell(s).

You can get combined fire alarm/intruder alarm panels too.

They are normally fail safe, ie an electro-magnet holds the door
open. If there is power failure, or an alarm, all the doors close, (ie
it does not run off the backup batteries.) Obviously there needs to
be a door closer.
Sometimes the door closer incorporates the door release magnet.