Hi all!
With the whole new intrusion interest here on IPVM I'm hoping someone would have an answer to my question.
Have any of you installed alarmed screens?
If you have what prevents a smart burglar from using a jumper wire with alligator clips to short out the wire loop and then just cutting the screen out?
There are several types of wire sensors like you mention here, and there are likely exceptions, but I know that many do not monitor continuity alone (unbroken circuit), but several types also are tuned for a specific electrical resistance.
If the wire doesn't equal a certain number (like if a jumper is added before a cut), it triggers an alarm too.
Yes you are right to a point, all modern alarm systems have an EOL (end of line resistor option) but that would only be at the end of the line. Meaning that if the wire in the screen was shorted it would be before the eol (on the same leg of the circuit). effectively bypassing the rest of the screen...)
Program the circuit as normally open with an end of line resistor at the end. If the wire is cut then the resistance is infinite and you get an alarm. If the wire is shorted out, then the panel no longer sees its normal resistance value and you get an alarm. Verify with your alarm panel which EOL values it supports (would possibly come with the panel) and be sure that the panel supports normally open zones (i would assume that they all do).
UM #2,
That is how most circuits are wired but that still won't resolve the issue at hand. Reason being because the wires running though the screen are running back and forth multiple times all before the eol. So shorting wouldn't make the panel aware.
If the zone is Normally Open, the normal state ("non-alarmed") is the resistance value. Any change from that state (such as a short or "closed" with no resistance) is an abnormal state and would give an alarm. So someone who puts an aligator clamp before the screen is essentially shorting out the zone and there would be a clsoed cirduit with no resistance and this would give an alarm.
That's true,
But the resistor isn't placed in the screen it's put at the end of the line, meaning that it would be placed at the point where the screen connects the the window frame. and if I had a window bay with a few windows there would only be one eol resistor. Each screen is just a little piece of the circuit. all before the eol.
No way the panel will know the difference...
Thank you all for the help so far!
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