© 2004 Bosch Security Systems
130 Perinton Parkway, Fairport, New York, USA 14450-9199
Customer Service: (800) 289-0096; Technical Support: (888) 886-6189
03/04
DS422i/DS426i Installation Instructions
P/N: 44974D Page 4
Figure R- Perimeter protection
Note that the beams are mounted so they cross each other. This way,
an intruder can not enter the area by walking between the units.
When installing multiple transmitters and receivers, test with all the
receivers powered-up, but with only one transmitter powered-up at a
time. A transmitter should set up only its receiver.
Receivers physically too close to a different system’s transmitters
may be set up even if the transmitter is not pointed at them (see
Figure T).
Figure T - Close proximity field problem
If a receiver is being set up by the wrong transmitter, the signals can
usually be eliminated by masking the sides of the transmitter and
receiver. Use electrician’s tape or duct tape inside each enclosure’s
window.
When installing these systems, remember that the infrared signal may
reflect off objects (e.g. glossy walls or floors) in the coverage area and
still set up the receiver.
A thorough walk test performed at several different points within the
coverage area will catch this problem. Re-aligning the units should
solve this problem.
The only way to insure proper continual protection is to perform
regular walk tests of the desired coverage area.
9.0 Application Tips
When using photoelectric detectors for motion detection, there are a
few installation techniques that will make the system more versatile.
9.1 Beam Stacking
Beam stacking gives a wall
of protection by stacking
several units at different
heights and providing an
alarm activation on the
blockage of only one pair of
beams (see Figure N for the
correct set-up technique).
Note that the system is
installed with alternating
transmitters and receivers at
each end. This eliminates the
possibility of a receiver being
covered by more than one
transmitter.
The maximum spacing between receivers (S) can be calculated by
dividing the distance between the transmitter and its receivers (D) by
20.
Therefore, if the distance between a transmitter and receiver is 100
ft. (30 m), the maximum spacing between receivers would be 100 ft.
(30 m) ÷ 20, or 5 ft. (1.5 m)
S = D/20 S = 100 ft. (30 m)/20 S = 5 ft. (1.5 m)
A potential problem when installing systems in a beam stack is “Near
Field Reflection.” Near field reflection is caused when a reflective
object is placed in the line-of-sight of the detectors and causes the
transmitted signal to be reflected to the wrong receiver (see Figure
P).
T1
R2
R1
T2
Figure P - Near field reflection
It may be desirable to have more than two sets of beams to create
taller stacks. This can be accomplished by adding receivers as shown
in Figure Q). Note that the beam from each transmitter is covering
two receivers.
T1
R4
R1
T2
R3
R2
Figure Q - Multi-system stack
9.2 Perimeter Protection
When protecting the interior of an installation, a good technique is to
mount the units at 90° angles around the coverage area (see Figure
R).
T1
T2
T3
T4
R1
R2
R3
R4
Figure N - Beam stack method
T1
R2
R1
T2
S
D
