Re: "Magnet tamper" for surface mount contact?

["Bill" <bill190nospam@xxxxxxxxx>]

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...)



"Jackcsg" wrote in message
> What you're looking for is called a "BMS" (Balanced Magnetic Switch) I
> believe both Ademco, and Sentrol have a model for the application.
>
> "Bill" wrote in message
>
> > 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.
> >
> >
>
>