Is there a surface mount contact which has some sort of tamper device if the magnet is unscrewed from the door? Manufacturer? Model number?
This would prevent the situation where there is a door which opens out, there is a surface mount contact on the door frame, a surface mount magnet on the door - then intruder attaches magnet to above contact in some manner, unscrews magnet from door, then opens door outwards.
So unscrewing the magnet from the door or unscrewing the covering over the magnet to then unscrew the magnet from the door would trip the contact...
FYI - This is when the intruder gains access through the ceiling or wall, but then exits through a door.
| > This would prevent the situation where there is a door which opens out, | > there is a surface mount contact on the door frame, a surface mount magnet | > on the door - then intruder attaches magnet to above contact in some | manner, | > unscrews magnet from door, then opens door outwards. | >
| > So unscrewing the magnet from the door or unscrewing the covering over the | > magnet to then unscrew the magnet from the door would trip the contact... | >
| > FYI - This is when the intruder gains access through the ceiling or wall, | > but then exits through a door. | >
I've only used them a few times on DEA inspected installs...yah I think they were around 100 bucks each...that was a few years ago too. Yep..Sentrols.
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| > | > This would prevent the situation where there is a door which opens | out, | > | > there is a surface mount contact on the door frame, a surface mount | > magnet | > | > on the door - then intruder attaches magnet to above contact in some | > | manner, | > | > unscrews magnet from door, then opens door outwards. | > | >
| > | > So unscrewing the magnet from the door or unscrewing the covering over | > the | > | > magnet to then unscrew the magnet from the door would trip the | > contact... | > | >
| > | > FYI - This is when the intruder gains access through the ceiling or | > wall, | > | > but then exits through a door. | > | >
I know. There's always that Indian Reservation that makes the BMS for the Government. They were paying about $42.00 a piece for them. I did buy a Sentrol version, for I think around $107.00 a piece.
I've read the specs on the balanced contacts, but don't see anything about how just unscrewing the magnet would trip an alarm?
I see that placing an additional magnet up by the contact would upset the magnetic balance and then trip the alarm, or unscrewing the magnet and then moving it closer to the contact and taping it in place would trip the alarm....
But I don't see where unscrewing the magnet and keeping it the same distance from the contact would cause an alarm.
I seem to recall that there were contacts on a UL grade AA system which had covers over the magnets. The contact and magnet were both about 2 inches by
4 or 5 inches and 2 inches deep. Both the contact and magnet had covers with tampers. If you removed the cover over the magnet, I think it would either drop the magnet away from the contact or place a barrier between the magnet and the contact. Attempting to remove the magnet from the door by removing the cover would cause an alarm.
I never installed any of these or had need to service them, so don't know if this is true or not. I was told that attempting to remove the cover from the contact or the magnet would trip the alarm. These also had three wire connections. (For UL system...)
You could always put another switch under the magnet and put that circuit on a 24 hr zone...like a recessed switch mounted under the mounted magnet...you'd need an ugly door cord though.
| > > This would prevent the situation where there is a door which opens out, | > > there is a surface mount contact on the door frame, a surface mount | magnet | > > on the door - then intruder attaches magnet to above contact in some | > manner, | > > unscrews magnet from door, then opens door outwards. | > >
| > > So unscrewing the magnet from the door or unscrewing the covering over | the | > > magnet to then unscrew the magnet from the door would trip the | contact... | > >
| > > FYI - This is when the intruder gains access through the ceiling or | wall, | > > but then exits through a door. | > >
On a balanced contact like Sentrol's 2707A, one simple solution is to mount the magnet so that the magnet mounting screws are covered by the switch when the door is in the closed position. The switch, by the way, has an optional tamper feature to detect removal of the switch from the door frame.
Some brands of balanced contacts have used two magnets, one attached to the cover of the magnet housing, one within the housing. Since the mounting screws are inside the housing, it becomes necessary to remove the cover to remove the magnet housing, which unbalances the magnetic field.
I've only seen some of the Governments version of the BMS that works in the manner of which you're speaking. Generally the biggest deterrent would be to affix the magnet with security screws.
Dohhhhh! Here I go again, trying to think of an expensive high tech solution to a simple problem...
What a great, inexpensive, and easy solution!
Very good suggestions! Cover magnet with contact or use security screws. (For doors which open out.) And of course use the triple biased contacts to prevent a second magnet from being used...
What's the possibility of replacing the current contact and magnet with recesssed button-style units? Example:
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The switch goes into a hole drilled into the door jamb, the magnet into a hole in the edge of the door; they can be placed anywhere around the perimiter of the door and are practically invisible and impossible to remove with the door closed.
Very possible for most situations except one. But also I like the added security of a 3 wire contact with tamper covers.
With the concealed contact, the wires are not accessible - so not to worry about anyone messing with the wiring.
And there are other tricks which can be used on an exposed 2 wire contact - like soldering the end of line resistor inside the contact, then anyone attempting to short the two wires would trip the alarm. If you have several doors and say a 1K EOL, I suppose you could use two 500 ohm resistors which would cover two doors or use a panel with a lot of zones.
What I have seen mostly so far as an intruder defeating a door contact is either to add an additional magnet, unscrew magnet from door and attach to contact, or short the wires. And this is only with your more "educated" intruders, which is quite rare (the educated part that is). So although it is unlikely you would ever have a visit from such a pro, I do think it is best to go beyond just using two wire surface mount contacts on doors which open out.
Using a 3 wire contact (N/O *and* N/C) will make it quite difficult even for the "educated" types to figure out what to do. But then there is still the problem with the magnet. I suppose if the contact is very close to the magnet (tight fitting door), you could remove the back cover from the magnet, glue the magnet to the door, then screw the cover over that. Then they unscrew the magnet, tape it to the contact above, but when they open the door, the magnet glued to the door would open out with the door. So they would just be taping the plastic case to the contact and not the magnet.
Actually there is a very simple way of finding a recessed door contact. But trying to defeat it with a magnet could get dicey... get the poles wrong and you may trip it.
A small magnetic compass will tell you the location and polarity of the sensor. Fortunately, most thieves are too stupid to bother trying to defeat the system. They mainly rely on the fact that the monitoring company can't possibly get a policeman on scene in the short amount of time it takes to do a typical residential burglary.
The advantage to using the recessed contacts is that they can't see where the contact is, or even IF it is, so unless they ring the entire door with magnets, they'll have a hard time defeating it.
Why don't you add another section to your FAQ's on all the different ways to defeat a system and put that out on your websit as well? You are such an asset to the industry Robert.
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