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RadEd
 |  | Magnetic alarm
< on 10/27/2003 6:55 PM >
|  | | | How do you know whether or not a door has a magnetic alarm on the other side and what can you do about it?
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Mister Hobbs
| | Re: Magnetic alarm
<Reply # 1 on 10/27/2003 7:39 PM >
|  | | | Posted by RadEd
How do you know whether or not a door has a magnetic alarm on the other side and what can you do about it?
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Without prior knowledge or some odd situation where there is such a gap at the top that you can see something, you won't.
Perhaps observing other areas that are protected in that manner would give a clue as to the rest of the area(s).
In order to know what is on the other side without a way to view it real-time or have prior access to it, you would have to resort to destroying something, from minor to major damage, in order to see.
You could take a telescoping mirror (and a light if necessary in that particular area) if the gap were large enough at the bottom of the door and peer upwards to get an idea.
That is still no safe bet because of the proliferation of flush mount ball and other projection switches that are not magnetic that can be in the door jamb, etc.
As far as "doing" something about it if you did know beforehand, that would depend on the type of magnetic switch that was being used. U.L. & D.o.D. approved "balanced" magnetic contacts you are not going to be able to do anything about. Then again, I would hope that you are not trying to circumvent a system that had that sort of protection or you would be looking at serious prison time if caught.
Regular magnetic "reed" switches can be circumvented in a couple/few ways with prior access or destructive (to the wall) techniques, etc., at times. No safe bet, depends on the system then too! If the system is good, it might go into alarm right then and there. If it is not so good, you can take a similar magnet from another switch you purchase and place it up there with some systems, usually beforehand (again, prior access, ain't life grand?) and this will keep it from going into alarm.
In incredibly basic (read stupid, low security) systems, it might be possible to jump it out if you have access to the terminals (assuming the reed switch is not sealed) or the wiring in the walls, etc.
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Mister Hobbs
| | Re: Magnetic alarm
<Reply # 2 on 10/27/2003 7:46 PM >
| | | | By the way, upon reflection, there is something that will give away protection on the other side of a door. It is not rare but is more likely to be seen on older systems which might very well still be in use.
That is a Shunt Switch. This is a simple lock mounted into the wall (I've seen them mounted into the door as well with a coiled cord on the other side so the wiring is not damaged from high traffic use.) that can be a single side disc (wafer) tumbler, double sided disc tumbler, Ace Tubular, Medeco or Abloy. If it is Medeco or Abloy, good luck turning it off. It's a simple on/off electrical switch which allows you to "shunt" whatever piece of protection is on the door or on the other side of the door so you can enter a given area without setting off time delays and whatnot on the system...so you can get to the panel to hit a code or turn a key there as well.
Sometimes these were mounted alone, all you see is the lockface of the switch, other times they had a rectangular mounting plate oriented vertically, which had a red and green light, etc.
If it is a stand alone, it is probably not tamper alarmed. If it has the plate, it may have a coiled spring (depressed) tamper switch behind that panel and when you remove it, guess what happens...
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Chainsaw
  
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| |  | Re: Magnetic alarm
<Reply # 3 on 10/27/2003 8:27 PM >
| | | | Most of the door alarms I've seen are magnetic reed switches. The reed switch is mounted in the frame of the door and a magnet is embedded in the door where it will line up with the switch. So, when the door is closed the magnet in the door pulls the reed switch closed. Opening the door causes the magnet to move away from the swtich and WOOT WOOT WOOT the circuit is broken and the alarm goes off.
You can keep that switched closed with your own magnet if:
You know exactly where the switch is.
You know which pole of the magnet will pull the switch closed and not push it open.
When well installed there is very little room between the magnet in the door and the switch to get your magnet in between them without removing some part of the molding. Typically the switch/magnet is installed on the "inside" meaning that if trying to open the door from outside you would have to dig through the frame somewhere to get your magnet up next to the switch.
If you can get a good look at the door frame you should be able to see the little round switch head, unless they painted over it. So, not seeing the switch doesn't mean there is no alarm.
Quid latine dictum sit, altum sonatur.
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