Is it? I've never heard of it. The average magnetic contact has an operating
gap in execss of 20mm. Newer ones will stretch to 80mm! That's some warped
door!!! As for wind... I have never known wind to cause a door contact to
operate. That is unless the door is blown open!
Door contacts are usually fitted in the door frame on the opening edge for
ease of wiring but can also be mounted in the head of the frame approx 6
inches from the opening edge. As a general rule the door should open a
maximum of approx 8 inches before the contact operates and the further from
the opening edge the more the door needs to open. On bolt hinged doors the
contact can also be fitted on the jamb edge.
Usine two detectors in parrallel is another idea but is messy. Dual-tec
detectors do the job well.
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
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 It's outdated by many other forms of setection such as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.
Smoke bombs eh?! Corr!
Burglar identifying paints?? Don't think so. You've been watching too much
Maybe you mean ID spraying? In which case, as we're on a DIY group, I don't
think it's worth mentioning as the minimum cost of registration and
instalation is around £5k!
A/T wiring has been standard since the 60's and is an absolute must. It's
not just there to warn of attack but also to give alert to damaged wiring
But it is if it does the job. In my time I have installed thousands of 3 PIR
systems with panels that have no more than a single knoxk circuit. They
rarely false alarms and always activated on intrusion.
I'm not having a pop at you NT. I'm just using your post as an example of
how wrong terminology and poor advice can cause more confusion that it's
worth. We're talking security here and it's not good to give outdated advice
and non-suitable idea's.
No worries :) If I'm wrong keep saying, and together we all learn.
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.
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.
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:
"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."
This explains why modern ones are reliable and effective, and
incorporate the tech you mentioned above:
It is around, just not popular. Google. Also, copper adhesive foil
used in lead window making can be used effectively.
Handbook of Loss Prevention and Crime Prevention,
"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 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."
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
The disorientation makes it take a long time to simply get back out of
the building, thus improving odds of arrest, as well as being visible
to passers by.
I did say if you had money to spend: this is not really your usual 2
up 2 down kit :)
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.
a must? why?
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.
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.
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.
No, still can't agree. My experience says different and I'd avoid them like
No, what's still around is self adhesive alluminium crap. Proper window foil
was lead and not self adhesive.
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.
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.
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.
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?!
Deter and prevent yes. Help catch - no. Not at all. A simple wip with a rag
and it's gone.
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?!
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
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
I've got to agree that glass-break detectors are one of the worst sources of
false alarm on any system that employs them. Just running an aluminium can
along a piece of glass in the property can cause them to activate. We hate
using them and try not to unless they're fitted in an office on the fortieth
floor of the block, but even these have sometimes been activated by pigeons.
Well I accept much of what you say, just 1 or 2 questions.
So its not popular but does still get used at times, and aluminium and
copper foils are still available. Looks like we agree.
It gets on both hands and clothes. You can wipe your hands but you
cant wipe goo off your clothes as easy as that. Those of us whove done
decorating know that you can be as careful as you like, paint still
tends to wander and turn up where its not expected.
Thus this black goo is likely to be on the burglar until they get
home. If the police turn up at time of incident and pick someone up,
either on premises or off, the presence of this same black goo is
useful evidence. It narrows down the suspects rapidly, leaves the
burglar with an explanation problem, and is one more piece of evidence
in the picture.
Ok, lets get back to basics here. Does Screwfix sell this as an anti-clime
paint or a "burglar identifying" paint?
Go one, answer that question but please keep your answer strictly to
information which can be found in the Screwfex book! i.e. from the title
description of the product (anti-climb paint)!
Another approach towards security is to use laminated glass in the
openings big enough for burgers to get in through. They'll have to
bash in numerous imes to get through, each time making a breaking
glass noise. They soon give up, as every glass smashing noise is a
real risk to being caught. Repeated smashing is a dead give away. But
retrofitting this isnt really a cheapie option.
Yes, a good idea and there is always the option of security film too.
Problem is that if they want to get in a simple large jemmy bar will not
only remove the glass but the whole frame too!
I've mentioned security film there but please be aware that for a proper
result it's not a DIY job. Most first timers mess it up and end up with dull
patches and creases all over the gaff.
I remember when my daughter was born 16 years ago I bought some
security film on a roll in Mothercare, and applied it to a low-level
window in our rear patio door - which was plain glass.
You are absolutely right about getting creases - even though I thought
I was taking care! I should have taken a bit more time.
Sending email to my published email address isn't
guaranteed to reach me.
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