Re: "Magnet tamper" for surface mount contact?

["Jackcsg" <nospam@xxxxxxxxxx>]

I've only seen some of the Governments version of the BMS that works in the
manner of which you're speaking. Generally the biggest deterrent would be to
affix the magnet with security screws.

"Bill" <bill190nospam@xxxxxxxxx> wrote in message
news:3pim8eFaickcU1@xxxxxxxxxxxxxxxxx
> 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.
> > >
> > >
> >
> >
>
>