On 09/10/2019 21:10, Andy Burns wrote:
ARW wrote:

A SAB's siren is powered via the control panel and the SCB's siren is
powered via it's internal battery.

0V is normally applied to the bell terminal on both to activate the
siren.

The removal of 12v to either will activate the tamper and the siren
will sound due it's internal batteries.

Given the bell-box is outside and difficult to reach, you'd expect them
to be more likely to have a dead battery, but I suppose in that case the
sounder wouldn't sound* after a power cut, so I assume most of the ones
causing nuisance have a dead internal panel battery?


[*] actually there was one last year that sounded like it was being
strangled/drowned when it went off, could have been the remnants of the
bell-box battery.

Yes, a dead internal battery is almost certainly the problem.

But bell boxes seldom use SLAs as their back up power.


--
Adam