No worries If I'm wrong keep saying, and together we all learn.

Indeed we all will.

That sounds different to the ones I've had experience with. They didnt
have anything like 20mm to play with, and proved to be useless. They
were affected by warp, wind, you name it. The ones that were
decommissioned were magnets and reed relays. But if things have moved
on, good, I gather they have.

No, basically they're still the same. A reed and a magnet. The operating gap
should always be 20mm minimum. Perhaps some cheaper makes have an
insufficient magnet though.

Some contacts have moved on a little though. ID contacts incorporate a chip
which is directly affected my a magnet. These are usually in 7/16 inch
bullet type contacts and are only suitable for use on ID systems.

Oh and we should all be using ID these days because not only is it much more
secure but it's also very easy and cheap to intall and offers much more
flexibility that conventional systems.

Third cover your desired area with more than one technology. Only when
both detect an intruder do you want the system to go off. Most sensors
are prone to some cause of false alarm or other.

Usine two detectors in parrallel is another idea but is messy. Dual-tec
detectors do the job well.

Yes, this is another way of implementing the above, rather than
implementing it at the control panel. Either way, 2 detection events
by 2 different technologies are needed to avoid false alarms.


Glass break sensors are useful (not foil strips).

With respect... glass breaks detectors are useless because the
ultra-sonic
sound they rely one (breaking glass) can be caused be many other natural
sources. Fridge motors is a good example! I remember in the early 80's
when
these bacame popular. We installed hundreds of them in schools, shops
and
the like. Then the kids discovered that if they through milk bottles
outside
the window the bloody alarm would activate! No, forget break glass
detectors.

Youre describing early ones, which were problematic as you say. Things
have moved on. All detectors have false trigger modes, these included.
What you describe is the result of using low tech detectors and using
a control panel that (wrongly) triggers from just one detection event.
If you use them with another detector type, with 2 events being
required for system trigger, you have a sound system. Or just use a
modern glass break detector with proper discrimination.

Here we go:

http://web.raex.com/~colombo/security/secmis9.htm

No, sorry, can't agree. They are still prone to false alarms. I know any
detector can false but these breakglass detectors are more prone. Put it
this way... they are almosy outlawed in the new ACPO (Association of Chief
Police Officers) policy.


"Older models were plagued by false alarms. This is because they did
very little filtering and even much less audio processing to tell the
difference between a valid sound and one that is normal to the
environment. More recent designs now use microprocessors to digitize
and process the audio sounds picked up in an environment. This enables
them to discern the difference between the sound of a window breaking
and that of a broken drinking glass."

No, still can't agree. My experience says different and I'd avoid them like
th eplague.

As for window foil. It's outdated by many other forms of setection such
as
curtain PIR's etc. You can't even buy the proper foil and blocks these
days.

It is around, just not popular. Google. Also, copper adhesive foil
used in lead window making can be used effectively.

No, what's still around is self adhesive alluminium crap. Proper window foil
was lead and not self adhesive.


Handbook of Loss Prevention and Crime Prevention,
Butterworth-Heinemann:

"In the past, foil tape was the most common way that security
installers electronically secured window glass. Although it is not as
common today, foil tape is still used by alarm installers who are
skilled enough to work with it. In fact, many of them swear that it
works better than any of the electronic devices--called glass-break
detectors--used by other installers.
"Metallic foil...is widely used to detect glass breakage in show
windows, doors, and transoms. When the glass cracks and breaks the
foil, it interrupts the low voltage electrical circuit and activates
the alarm"

And what year was that written? 1904?! Trust me, no alarm company uses foil
these days. OK odd job yes but it's just not used as a general rule. It's
not been in the course syllabus for many years.

"The presence of foil tape on windows is an automatic sign that a
burglar alarm system is employed on the premises. Most burglars would
rather not break into a facility that has one."

And again, when was that writtin? 1906?! It's true of the 70's but today all
premises are secured and foil is long ceased to be used.

Smoke bombs eh?! Corr!

Yup, they work by disorientating the burglar, and making them realise
they are out of control of the situation. If you have a large valuable
premises, using these by entrances halls stops many burglaries in
their tracks.

I was actually being sarcastic. Smoke Bombs as you call them are actually
Smoke Generators. They produce smoke by heating glycol - like a disco smoke
machine - same stuff. They are on standby when the alarm is set and activate
the pump when the alarm activates. The most well known system is Smoke Cloak
but these days theyre are "copies". Smoke Cloak was first shown around 1887.

Yes, they're bloody effective but again, we're on a DIY group here and so
it's unlikely to be of any use. I do though admit to having one installed in
my workshop/garage at home. Expect to pay upwards of £400 for one, maybe
more for a decent one. Refills of glycol are around £20 and you'll need
plenty cos you'll show it off to all your mates!

While on the subject... smoke generators are not up to much after a door or
window is left open as the smoke depletes very quickly. Better machines iave
a sensor which, when the smoke thins out, re-activated the machine to top up
the smoke. For this reason your suggestion of installing them in entrance
halls is a no-no. They're mainly used to secure area's "not yet intruded"
thus making entrance to that area very difficult. Computer rooms in office
buildings are a good example.

Burglar identifying paints?? Don't think so. You've been watching too
much
007!

http://www.screwfix.com/app/sfd/cat/...52567&id=16822

That's anti-clime paint - not identifying paint! So, it marks the burglars
hands black. Does that mean that when I next do an oil change on my car and
end up with black hands I'd better avoid being seen in public?!

There are also more technological ones available, which stain the skin
indelibly, but the simple cheap option above is suited to diy use on
drain pipes etc. They both deter and help catch afterwards.

Deter and prevent yes. Help catch - no. Not at all. A simple wip with a rag
and it's gone.

Finally tamperproof wiring is a bonus to protect against the more
determined attackers, but you dont need this in most cases.
A/T wiring has been standard since the 60's and is an absolute must.

a must? why?

How about when you have someone in your house you don't really know?
Decorator, gas man, daughters boyfriend. Wouldn't you like to know when and
if the PIR's, for example, had had their lids removed?! Or what about when
you nic a cable doing something. Wouldn't you like to know there and then
instead of waiting till you try and set the alarm and then have to wonder
where the cut may be?! How about British Standards which have stipulated A/T
wiring since 1980 when the standard was first introduced!

Or how about someone gettign a ladder up to your bell box, removing the lid
and cuting th ebell feed. Wouldn't it be nice to know?!

etc?

See above

My own experience with PIRs makes that hard to imagine. Perhaps either
youre using PIRs that require 2 events to trigger, or use dual
technology, or else PIRs have suddenly come a long way?

Over to you.

In the last 15 years alarm panels and detectors have moved on so much that
they are now very good. Ducl-tec, pulse count, double knock and ID have all
helped.

Even so, like I said I have installed systems before that which have been
nothing but well behaved. It's down to good engineering practice, common
sense and not buying cheap. In 1990 you could buy a UK made PIR for £6.
£4.50 if you bought 50 or more. I bought none, instead choosing to stick to
the old faithful ones that had been used for years previous. The company who
made the cheap £4.50 PIR's went pop after just two years! Says it all. Buy
cheap and not only will you have to buy twice but you'll have loads of grief
too.