protective circuits is run out through the switch hole
(fig. 8-20). There should be no more than 1/4-inch (0.6
cm) space for windows and 1/8-inch (0.3 cm) for doors
between the two sections of the detector.
4. Be certain there is enough space between the
window and its frame (or door and its frame) when each
is closed; that is, there must be enough space (usually
equaling 1/16 inch or 0.16 cm) for the protrusion of both
sections when they meet.
5. A switch and magnet are installed preferably in
the top of the window and underside of the upper
window casing, where they will be least noticeable (fig.
8-21). If the window frame is not thick enough to accept
the magnetic section of the detector, the detector can be
mounted in the side frame.
Conductive Foil on Glass Doors
A self-adhesive foil block (terminator) on the door
is connected to a similar unit on the doorframe by a
short length of flexible cord to allow for door
movement (fig. 8-22). The foil is connected in the
positive conductor of the protective circuit and is
adhered to the glass parallel to and about 3 inches (7.6
m) from the edge of the glass, using recommended
varnish. Breaking the glass breaks the foil and opens
the circuit. A double circuit of foil may be taken from
the foil block to provide more coverage. Coiled,
retractable cords are available for use between foil
blocks to allow for sliding-door travel.
Conductive Foil on Picture Window
Where a window does not open, a single run of foil
is connected to a foil block on the glass, frame, or wall
(fig. 8-23). When the foil crosses over a frame
member, a piece of plastic electrical tape should be
used to provide an insulated crossover surface for the
Complete Glass-Door Protection
A glass door with a glass transom may be protected
by a combination of magnetic contacts and foil (fig. 8-
The recessed plunger detector shown in figure 8-
25 is mounted so that the door or window will contact
the plunger at the tip and push the plunger straight in.
Therefore, the area of the window or door that
depresses the plunger should have no slots, cutouts, or
step-downs into which the plunger might slip. The area
also should be hard and free of rubber or vinyl that
might be weakened by the plunger and consequently
allow the plunger to open. For protecting doors,
plunger type of detectors should be mounted only in
the doorframe on the hinge side of the door.
In cases where it is difficult to protect a window or
door by mounting any of the direct type of detectors, the
area directly inside the door or window can be protected
with interior space detectors, such as a floor-mat detec-
tor (fig. 8-26) or an ultrasonic motion detector (fig. 8-27).
Floor-mat detectors are easily concealed under
rugs at doors, windows, top or bottom of stairways, or
any other area onto which an intruder is likely to step.
Light pressure on the mat triggers the alarm.
There are also rolls of super-thin floor matting that
can be cut to any desired length. These rolls can be used
on stair treads and in areas near sliding glass doors or
other larger glass areas, entrance foyers, and so forth.
In households with unrestricted pets, these mats are
almost useless since the pets roam around the home
and are certain to step on one of the mats and trigger the
Figure 8-20.Recessed magnetic contacts in door.