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From: "Michael A. Terrell"
Subject: Re: Radar basics?
Date: Sat, 19 Oct 2002 23:46:29 -0400
Organization: Do I have to? Well, Ok. If you insist!
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Dave VanHorn wrote:
> > Some high end PIR detectors have a microwave detector built it to
> > prevent false alarms from air currents when the heat or AC kicks in.
> Yep. Dual-Tek is one brand. A fairly good idea, though it also means a lot
> more components to fail.
> > I used some on a college campus a few years ago. The microwave sensor
> > kicks in for a fraction of a second to look for motion, then shuts down
> > if it doesn't find anything. That makes it harder for someone to locate
> > and disable the security system.
> I never worked with a switched one. Interesting idea.
> I always used overlapping patterns, and a few tricks of the trade to protect
> the system.
> Cheap keyswitch on a plate outside, with lit leds that change when the
> system is armed or not.
> However, picking the cheap lock and rotating the switch will not have the
> expected result.
> Mount the sensors on interior walls, and never run wiring outside that area.
> Pop a sensor or two above the ceiling tiles in sensitive areas.
> Wire running up a wall to a bell box. Of course the wire has nothing to do
> with the bell box at all, and it would be a bad idea to significantly alter
> it's resistance.
> Always, keep the control panel in a difficult spot. There's few control
> panels that will survive a hit from a fire axe.
> Never did this one, but a bad panel, mounted in a visible spot with working
> LEDs would be an easy (and wrong) target.
> The basic idea is to give them what looks like an easy way in, that is in
> fact sensored so that they trip the system while they are still outside.
> The visible sensors may or may not be the active ones, and there are always
> more sensors that you won't see.
These were mounted in the equipment rooms, along with the fire alarm
panels. A concrete building with the sensors aimed at the windows and
doors, all mounted on interior walls. If it weren't for the liability,
it would be fun to mount a fake panel with a small charge to blow it off
the wall when someone tampers with it. I was on the campus to install
the computer networking and MATV systems as a subcontractor when they
had troubles with both alarm systems so I had to clean up their early
wiring and finish them, as well.
Michael A. Terrell
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