On 10/10/2019 07:49, polygonum_on_google wrote:
On Wednesday, 9 October 2019 21:00:38 UTC+1, ARW wrote:
On 09/10/2019 12:33, dennis@home wrote:
On 09/10/2019 10:26, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* dennis@home wrote:
On 08/10/2019 11:20, Dave Plowman (News) wrote:
In article ,
Â*Â*Â*Â* alan_m wrote:
My bell box has a rechargeable battery that is also trickle charged
in my wired system via the alarm panel. My bell box also has red
flashing LEDs so a self contained non-rechargeable battery may not
last that long.

The tamper circuit in a bell box is often a spring loaded mechanical
switch which when the box is removed from the wall is activated.

I thought the bell box battery is only there so it will sound if it or
the wiring to it is tampered with. Under other circumstances, the
panel supplies the ringing volts to it - either from mains or its
battery.


Self Actuating Bells do not ring whenÂ* voltage is supplied from the
panel. The 12v from the panel stops them ringing and charges the
battery.

OK.

When an alarm condition exists the 12V is removed and they bell rings
until it comes back or the battery goes flat or if its a modern one a
timer expires.


Only cheap and nasty DIY alarms need 12V to operate the bell.
If you have one then get rid of it as it takes seconds to cut the wires
and then there is no external bell.

But if you remove the 12v the sounder sounds?

It does on a decent one.


No expert on alarm internals since I've only ever followed a wiring
diagram. But with your method, it would mean the sounder no longer works
if the internal battery is kaput?

That's why you can test them.

Its how all the bell boxes on banks work so it can't be the worst way.
No banks use one that rings when it is powered by 12v in an alarm
condition.

I have actually installed some for Chubb alarms but it was a long time
ago and I quit as I didn't like the training bloke as he was getting
things wrong about mains and didn't like being corrected.

It was my first proper job before I moved the GEC telecomms.


The old fashioned strobes may be powered from the box, mine are, they
take too much power for the battery.

Its not the same 12V that operates the rest of the box.

Thing is the bell box should be situated where it's difficult to get at.
Which means changing it or the battery equally difficult?

The battery is fine for years.
Not all buildings have somewhere difficult to get to.


And anyone who feeds it with accessible cabling should be shot. ;-)


crowbar, rip box off wall cut wires and one that needs power from the
panel goes quiet.


Both SABs and SCBs should still ring if ripped from the wall.

It would also set of the internal alarm and any other bell boxes.

I though high density PU foam was de-rigueur for that these days.

It's also a good bet that it would also set off an alarm signal to a
monitoring company.

BTW cutting the telephone wires on a proper monitored system also
actives the monitoring company.

Mind you opening one door without first closing another door on an unset
alarm can also set of a silent alarm in some houses BTDTGTTS. The police
were there in about 3 minutes.

How will that work when it becomes snap the fibre?

Same way if monitoring sends a ping and doesn't get a response. They try
to ring the alarm contact number(s) and if no response (or the duress
code is given) a priority police visit.

--
Regards,
Martin Brown