After many years of disuse, I recently went to work to get the alarm systems working. What I found was surprising.
Out of 23 alarm sensors on the first floor (we have a LOT of windows and a garage) 9 were failed. You could open the front door and several windows and no alarm at all.....so much for trusting alarm systems.
One door was not even wired. Nothing.
Turns out that the contacts within the tiny glass encased "reed switches" that are magnetically closed (and open when the magnet moves away) can sort of "spot weld" themselves in place, perhaps due to chronic current flow (galvanic deposition of metal?) or due to a surge of current due to induced flows of current from nearby lightning strike...according to what I read on the net. I found MANY reed switches that were "stuck". Most of them were made workable again by banging pretty hard on the plastic case with a metal tool. One broke (shattered) under that "repair" and had to be replaced, but many were salvaged.
I also learned that it is fairly easy for an astute criminal to get a very powerful magnet and stick it to your window near where the sensor is detected -- thus guaranteeing that the sensor will stay inactivated while he opens the window.....
We also have a motion alarm which would hopefully give us an additional line of defense, but my point is that it is very common for alarm systems that are not painstakingly checked, to fail. And thus you might very well have an intruder in the house without any alarm....
food for thought, and action.
Out of 23 alarm sensors on the first floor (we have a LOT of windows and a garage) 9 were failed. You could open the front door and several windows and no alarm at all.....so much for trusting alarm systems.
One door was not even wired. Nothing.
Turns out that the contacts within the tiny glass encased "reed switches" that are magnetically closed (and open when the magnet moves away) can sort of "spot weld" themselves in place, perhaps due to chronic current flow (galvanic deposition of metal?) or due to a surge of current due to induced flows of current from nearby lightning strike...according to what I read on the net. I found MANY reed switches that were "stuck". Most of them were made workable again by banging pretty hard on the plastic case with a metal tool. One broke (shattered) under that "repair" and had to be replaced, but many were salvaged.
I also learned that it is fairly easy for an astute criminal to get a very powerful magnet and stick it to your window near where the sensor is detected -- thus guaranteeing that the sensor will stay inactivated while he opens the window.....
We also have a motion alarm which would hopefully give us an additional line of defense, but my point is that it is very common for alarm systems that are not painstakingly checked, to fail. And thus you might very well have an intruder in the house without any alarm....
food for thought, and action.