We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

"Stuart Noble" wrote in message
...
We had a power cut here for about 3 hours just after midnight (yes, I know
I'm not the only one!) which set off a neighbour's burglar alarm. He
wasn't able to turn it off and the thing went on and on for well over 2
hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

On my oldish system there is a battery in the alarm control box which takes
over when the mains power is cut thus maintaining the system so in effect it
does not know that there has been a power cut.
If this battery is dead or missing the wall box thinks that the alarm has
been triggered as soon as the mains power goes off
These batteries should last for at least 5 years but often get forgotten
until a power cut occurs

The alarm box on the wall outside has in my case a capacitor which runs the
noisy bit for however long until the box in the house is reset. the system
then recharges the capacitor

Tony

On Mar 28, 12:23*pm, Stuart Noble
wrote:
We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

Mine has a battery backup in the main control box. This should keep
it going for quite a while in the event of a power failure. Once the
battery is dead, I guess the bell box will trigger, thinking that
someone has been tampering with the power supply. The bell box has a
built in battery which will keep the alarm sounding for a while :-(

I think mine has a setting which allows you to alarm on power
failure. Maybe your neighbour has this feature and its on (or maybe
they just dont have a battery backup).

Alan

On Mar 28, 12:47*pm, AlanC wrote:
On Mar 28, 12:23*pm, Stuart Noble
wrote:

We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

Mine has a battery backup in the main control box. *This should keep
it going for quite a while in the event of a power failure. *Once the
battery is dead, I guess the bell box will trigger, thinking that
someone has been tampering with the power supply. *The bell box has a
built in battery which will keep the alarm sounding for a while :-(

So, are the batteries in the bell box designed to last longer than the
ones in the control box? If the system hasn't been maintained and the
control box battery is dead, chances are the one in the bell box will
be too. Anyone?

MBQ

On Mar 28, 12:44*pm, "TMC" wrote:
"Stuart Noble" wrote in message

...

We had a power cut here for about 3 hours just after midnight (yes, I know
I'm not the only one!) which set off a neighbour's burglar alarm. He
wasn't able to turn it off and the thing went on and on for well over 2
hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

On my oldish system there is a battery in the alarm control box which takes
over when the mains power is cut thus maintaining the system so in effect it
does not know that there has been a power cut.
If this battery is dead or missing the wall box thinks that the alarm has
been triggered as soon as the mains power goes off
These batteries should last for at least 5 years but often get forgotten
until a power cut occurs

The alarm box on the wall outside has in my case a capacitor which runs the
noisy bit for however long until the box in the house is reset. the system
then recharges the capacitor

What size capacitor is that? How long is "however long"?

MBQ

"Man at B&Q" wrote

************************************************** **
So, are the batteries in the bell box designed to last longer than the
ones in the control box? If the system hasn't been maintained and the
control box battery is dead, chances are the one in the bell box will
be too. Anyone?
************************************************** *


I just upgraded my alarm system including the bell box.
The battery in the old bell box was still active - the system was 12 years
old (from the stated install date).
I had replaced the panel battery at 2 yearly intervals (since we took the
place on 7 years ago) as a precaution.

Phil

In message , Stuart Noble
wrote
We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well
over 2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)


The alarm would only go off if the backup battery in the control panel
is dead, or dying. In my experience the battery will still show 12V+
terminal voltage but is unable to cope with the power drain when the
mains goes off. I now replace my battery every 2/3 years.
--
Alan
news2006 {at} amac {dot} f2s {dot} com

AlanC wrote:
On Mar 28, 12:23 pm, Stuart Noble
wrote:
We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

Mine has a battery backup in the main control box. This should keep
it going for quite a while in the event of a power failure. Once the
battery is dead, I guess the bell box will trigger, thinking that
someone has been tampering with the power supply. The bell box has a
built in battery which will keep the alarm sounding for a while :-(

I think mine has a setting which allows you to alarm on power
failure. Maybe your neighbour has this feature and its on (or maybe
they just dont have a battery backup).

Alan

Thanks
Well, I imagine the battery in the bell box is working fine judging by
last night's performance, so it sounds like the one in the control box
is naff. What type of battery is it likely to be? Easy to find?

In message , Stuart Noble
wrote

Well, I imagine the battery in the bell box is working fine judging by
last night's performance, so it sounds like the one in the control box
is naff. What type of battery is it likely to be? Easy to find?

Yep, easy to find

Towards the smaller end of range of:

http://www.maplin.co.uk/module.aspx?ModuleNo=19363&doy=28m3
--
Alan
news2006 {at} amac {dot} f2s {dot} com

"Stuart Noble" wrote in message
...
AlanC wrote:
On Mar 28, 12:23 pm, Stuart Noble
wrote:
We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

Mine has a battery backup in the main control box. This should keep
it going for quite a while in the event of a power failure. Once the
battery is dead, I guess the bell box will trigger, thinking that
someone has been tampering with the power supply. The bell box has a
built in battery which will keep the alarm sounding for a while :-(

I think mine has a setting which allows you to alarm on power
failure. Maybe your neighbour has this feature and its on (or maybe
they just dont have a battery backup).

Alan

Thanks
Well, I imagine the battery in the bell box is working fine judging by
last night's performance, so it sounds like the one in the control box is
naff. What type of battery is it likely to be? Easy to find?

Its an intruder alarm battery from an alarm company
Mine was from Abel Alarms over the counter about 8ukp
Maplin sell them
Ebay has them
They are the same as many motor scooter batteries

Tony

"Man at B&Q" wrote in message
...
On Mar 28, 12:44 pm, "TMC" wrote:
"Stuart Noble" wrote in message

...

We had a power cut here for about 3 hours just after midnight (yes, I
know
I'm not the only one!) which set off a neighbour's burglar alarm. He
wasn't able to turn it off and the thing went on and on for well over 2
hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

On my oldish system there is a battery in the alarm control box which
takes
over when the mains power is cut thus maintaining the system so in effect
it
does not know that there has been a power cut.
If this battery is dead or missing the wall box thinks that the alarm has
been triggered as soon as the mains power goes off
These batteries should last for at least 5 years but often get forgotten
until a power cut occurs

The alarm box on the wall outside has in my case a capacitor which runs
the
noisy bit for however long until the box in the house is reset. the system
then recharges the capacitor

What size capacitor is that? How long is "however long"?

MBQ

Difficult for me to tell as I suppose that I would have to undo the box on
the wall to check the size and then switch off the mains power disconnect
the battery in the control box and time the alarm whilst dodging objects
being thrown by the neighbours and explaining to swmbo why am I doing this

Sorry can't help

Tony

TMC wrote:
"Stuart Noble" wrote in message
...
We had a power cut here for about 3 hours just after midnight (yes,
I know I'm not the only one!) which set off a neighbour's burglar
alarm. He wasn't able to turn it off and the thing went on and on
for well over 2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut?
How does it differentiate between that and somebody "tampering" with
its innards?
I'm off for a snooze now....:-)

On my oldish system there is a battery in the alarm control box which
takes over when the mains power is cut thus maintaining the system so
in effect it does not know that there has been a power cut.
If this battery is dead or missing the wall box thinks that the alarm
has been triggered as soon as the mains power goes off
These batteries should last for at least 5 years but often get
forgotten until a power cut occurs

The alarm box on the wall outside has in my case a capacitor which
runs the noisy bit for however long until the box in the house is
reset. the system then recharges the capacitor

That's right. I might be Stuart's neighbour, cos we had exactly the same
problem over Easter - control panel back-up cell was utterly knackered, but
sadly the alarm box back-up was able to keep going for hours. New 12v
sealed cell on order now.

On Mar 28, 1:00*pm, "Man at B&Q" wrote:
On Mar 28, 12:47*pm, AlanC wrote:





On Mar 28, 12:23*pm, Stuart Noble
wrote:

We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

Mine has a battery backup in the main control box. *This should keep
it going for quite a while in the event of a power failure. *Once the
battery is dead, I guess the bell box will trigger, thinking that
someone has been tampering with the power supply. *The bell box has a
built in battery which will keep the alarm sounding for a while :-(

So, are the batteries in the bell box designed to last longer than the
ones in the control box? If the system hasn't been maintained and the
control box battery is dead, chances are the one in the bell box will
be too. Anyone?

MBQ- Hide quoted text -

- Show quoted text -

OK, when I said battery, I actually meant power supply. I am not sure
if its an actual battery or (as someone else has mentioned) a
capacitor (I suspect its actaully a capacitor).

If the power fails and the control panel battery is OK, then I would
guess that the control panel will still be providing power to the bell
box, which will still charge the capacitor. When the control panel
battery eventually dies, the capacitor will power the bell box, which
will annoy the neighbours!

Alan

On 28 Mar, 17:18, Owain wrote:
Stuart Noble wrote:
We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.

IIRC it's illegal under noise abatement legislation for intruder alarms
not to have a 20 minute max cut-off time on the audible sounder.

Mine has a timer to meet these regs, but I guess a capacitor value
selected against the known current drain would have the same effect,
though it might be difficult to convince a jobsworth with a stopwatch
of this.

Environmental Health would probably be the enforcement authority but are
unlikely to do much unless it keeps happening.

I think you're supposed to provide the constabulary with either the
name of someone they can call to turn it off in your absence (since
they don't respond to alarms not connected to a call centre without
some other evidence), or your keys so that they can do it themselves.
I wonder how many people have done either, especially the latter?

Chris

On Fri, 28 Mar 2008 12:23:21 GMT, Stuart Noble
wrote:

We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.

Aren't they supposed to turn themselves off after 20 minutes or so,
like car alarms?

"Owain" wrote in message
...
Stuart Noble wrote:
We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm. He
wasn't able to turn it off and the thing went on and on for well over 2
hours until it ran out of juice.

IIRC it's illegal under noise abatement legislation for intruder alarms
not to have a 20 minute max cut-off time on the audible sounder.

Environmental Health would probably be the enforcement authority but are
unlikely to do much unless it keeps happening.

Owain

I see that boxes available on the web have an auto cut-off timer. Mine is a
good few years old so do you know if regs would require retrofit or is it
only for new installs?

Tony

In message , Peter Johnson
wrote
On Fri, 28 Mar 2008 12:23:21 GMT, Stuart Noble
wrote:

We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.

Aren't they supposed to turn themselves off after 20 minutes or so,
like car alarms?

In this case the alarm wasn't triggered normally.

The time-out is implemented in the control box which has no power
because the backup battery is dead. The bell rings because of the anti
tamper circuit. Remove power from the wires supplying the bell box and a
relay (mechanical or solid state) trips and applies the power from the
back-up battery in the bell box to the bell.

If the battery in the control box were okay the alarm wouldn't have
normally triggered in the first place and even if it had a time-out
would have cut in.

On my 15 year old system the time-out period is configured by the user
during the programming mode of operation. I've set mine to 5 minutes for
the bell. The strobe light continues until reset by the user.

--
Alan
news2006 {at} amac {dot} f2s {dot} com

Alan wrote:
In message , Peter Johnson
wrote
On Fri, 28 Mar 2008 12:23:21 GMT, Stuart Noble
wrote:

We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.

Aren't they supposed to turn themselves off after 20 minutes or so,
like car alarms?

In this case the alarm wasn't triggered normally.

The time-out is implemented in the control box which has no power
because the backup battery is dead. The bell rings because of the anti
tamper circuit. Remove power from the wires supplying the bell box and a
relay (mechanical or solid state) trips and applies the power from the
back-up battery in the bell box to the bell.

If the battery in the control box were okay the alarm wouldn't have
normally triggered in the first place and even if it had a time-out
would have cut in.

On my 15 year old system the time-out period is configured by the user
during the programming mode of operation. I've set mine to 5 minutes for
the bell. The strobe light continues until reset by the user.


Thanks, Alan. I've spoken to the neighbour who is mighty relieved that
it should be a simple job to fix. He apparently cut the cables to the
bell box in a panic, so that'll be a little extra job.
Kind of spooky knowing your alarm can go off even when you haven't set
it, that it can go on for hours, and there's nothing the owner can do
about it. I suppose modern keypads have a low battery warning

In message
,
AlanC writes
OK, when I said battery, I actually meant power supply. I am not sure
if its an actual battery or (as someone else has mentioned) a
capacitor (I suspect its actaully a capacitor).
It's a battery.

If the power fails and the control panel battery is OK, then I would
guess that the control panel will still be providing power to the bell
box, which will still charge the capacitor. When the control panel
battery eventually dies, the capacitor will power the bell box, which
will annoy the neighbours!
Intruder alarms should only sound for a certain period of time, IIRC
it's 30 seconds for car alarms and 20 minutes for a building. It can be
considered a nuisance under environmental protection laws if it sounds
for longer and it's a nasty fine if they decide to prosecute.

http://www.castlemorpeth.gov.uk/serv...ion/noise_poll
ution/Documents/AlarmLeaflet.pdf

Local council officers with the police have the power to force entry to
premises, silence nuisance alarms and bill the owner for the privilege!


Alan

--
Clint Sharp

In message , Stuart Noble
wrote


Thanks, Alan. I've spoken to the neighbour who is mighty relieved that
it should be a simple job to fix. He apparently cut the cables to the
bell box in a panic, so that'll be a little extra job.
Kind of spooky knowing your alarm can go off even when you haven't set
it, that it can go on for hours, and there's nothing the owner can do
about it. I suppose modern keypads have a low battery warning

Sod's law will now operate.

Make sure that your neighbour has the alarm instructions to hand. Make
sure that he understands them before opening up the control panel. He
may need to re-program the box. My alarm manual was a very poor
translation into English from a very poor set of instructions in Chinese


There will be an anti tamper switch (on a spring) in the control box
that will trigger the alarm when the cover of the control box is
removed. It may be sensible to replace the battery (without removing the
mains) before the wires to the bell box are repaired - or else panic
number two will set in.

--
Alan
news2006 {at} amac {dot} f2s {dot} com

In article , Stuart Noble
writes

Thanks, Alan. I've spoken to the neighbour who is mighty relieved that
it should be a simple job to fix. He apparently cut the cables to the
bell box in a panic, so that'll be a little extra job.
Kind of spooky knowing your alarm can go off even when you haven't set
it, that it can go on for hours, and there's nothing the owner can do
about it. I suppose modern keypads have a low battery warning

In modern systems both panel and bell boxes have timeouts to avoid this
sort of problem. To avoid a reoccurrence, your neighbour could replace
the bell box with a modern one or just swap over the electronics,
sounder and strobe. This low cost one would do the job:
http://cpc.farnell.com/jsp/level5/mo...cpc/276584.xml

That is as well as changing the panel battery of course, 2 years is the
routine replacement period.

Screwdriver, ladder and ear plugs could have shortened the 2 hours of
night time fun.
--
fred
Plusnet - I hope you like vanilla

In article ,
says...
We had a power cut here for about 3 hours just after midnight (yes, I
know I'm not the only one!) which set off a neighbour's burglar alarm.
He wasn't able to turn it off and the thing went on and on for well over
2 hours until it ran out of juice.
Question is, how does a well designed alarm deal with a power cut? How
does it differentiate between that and somebody "tampering" with its
innards?
I'm off for a snooze now....:-)

What will have happened is that self actuating bell has activated due to
the control panel's battery failing.
The battery in the control panel should be designed to keep the system
active in a standby condition (or set) for upto 20 hours. After this
time, it will no longer provide the hold-off supply to the bell box,
which will activate itself. This bell should have a 20-minute timer on
it after which it should cut out.

From the sounds of it, he needs a new battery, the system will need
servicing as it's probably not been done, and he'll need a new bell box
that is compliant with current regulations.
--
Alex Threlfall
Cyberprog New Media
www.cyberprog.net

In article ,
Stuart Noble writes:

Thanks, Alan. I've spoken to the neighbour who is mighty relieved that
it should be a simple job to fix. He apparently cut the cables to the
bell box in a panic, so that'll be a little extra job.
Kind of spooky knowing your alarm can go off even when you haven't set
it, that it can go on for hours, and there's nothing the owner can do
about it. I suppose modern keypads have a low battery warning

Some do, but it's a battery test function which would have saved
you from this one. This switches the alarm to run from battery for
a period of time. If it hits a low battery state during that, it
generates a battery failure warning, which is subtley different from
a low battery warning (which isn't necessarily a faulty battery).
The default programming for mine is to run the battery test once
a day, but you can change this, and also make it do it on demand.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

I'm not so sure that external audible alarms are any use anyway since
everyone seems to ignore them.

I'm actually thinking of installing an internal (very loud) alarm on
the basis that when I worked in a nuclear facility we had an internal
alarm to warn us if the radiation levels exceeded a certain level.
The alarm was tested every week and believe me, everyone left the
building very quickly because the noise was horrific. So I would
expect any burglar would do the same.

On Fri, 28 Mar 2008 20:48:01 +0000, Owain
wrote:

If the old bell box doesn't have a strobe it would be well worth
replacing it with one that does - (a) it is easier to locate which house
has the activated alarm; (b) the strobe can continue after the time
limit, providing a warning to the returning occupant that someone may
have been (or may still be) inside the house.

The trouble with a strobe is that if it's flashing away for hours on
end there's a very strong likelihood that there's nobody at home, and
that it's safe to break in.

--
Frank Erskine

On Sat, 29 Mar 2008 16:36:56 +0000, Owain wrote:

On the other hand, a warning before you go into a house that might have
a burglar still inside is a very valuable increase in personal security.

That could be achieved by a LED in a corner of a window, rather than a
bright light flashing away on a box on the side of the building visible
from a long distance.

--
Cheers
Dave.

On 29/03/2008 15:24 Frank Erskine wrote:

The trouble with a strobe is that if it's flashing away for hours on
end there's a very strong likelihood that there's nobody at home, and
that it's safe to break in.

A few months ago we had a power cut. One of the houses nearby was
unoccupied but fully furnished and the strobe on their alarm flashed for
the following six weeks...

--
F

In article ,
writes:
On 29 Mar,
Frank Erskine wrote:

On Fri, 28 Mar 2008 20:48:01 +0000, Owain
wrote:

If the old bell box doesn't have a strobe it would be well worth
replacing it with one that does - (a) it is easier to locate which house
has the activated alarm; (b) the strobe can continue after the time
limit, providing a warning to the returning occupant that someone may
have been (or may still be) inside the house.

The trouble with a strobe is that if it's flashing away for hours on
end there's a very strong likelihood that there's nobody at home, and
that it's safe to break in.

That's why my strobe is linked to the bell, and stops when the bell stops.

That's quite commonly done. Even when the panel does have a
separate strobe output, many installers prefer to connect
the stobe to the siren output instead for this reason.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sat, 29 Mar 2008 05:48:29 -0700 (PDT), ac1951
wrote:

I'm not so sure that external audible alarms are any use anyway since
everyone seems to ignore them.

I'm actually thinking of installing an internal (very loud) alarm on
the basis that when I worked in a nuclear facility we had an internal
alarm to warn us if the radiation levels exceeded a certain level.
The alarm was tested every week and believe me, everyone left the
building very quickly because the noise was horrific. So I would
expect any burglar would do the same.

All very well - but most alarms are false alarms IMHO.

I'm glad the posters here maintain their systems properly but where I
live - during a power cut there are always several alarms going off.

M.