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Chapter 2: Installation
11
2.11 Multiple Sensors
The Model 1108 may have more than one sensor connected to
the same alert input, as long as the normal condition for each
sensor on the same alert input is identical (either all N.O. or all
N.C.). However, only one remote temperature sensor can be
used on each input.
When wiring several normally closed sensors on one input,
they must be connected in series. Connect one lead from the
first sensor to the numbered screw of the alert input. Next, take
the other lead from the first sensor and connect it to one lead
from the next sensor. Continue connecting sensors end-to-end
until you have connected all of your sensors. Take the second
lead from the last sensor and connect it to the ground screw on
the Model 1108. See Figure 2-8. Multiple N.C. sensors are
typically magnetic reed switches to monitor the security of
windows and doors.
~
~
~
~
Multiple normally-closed
sensors wired in series.
(Example shown using Input 3.)
Alert condition
occurs when a
switch is opened.
23456781
GND GND GNDGND
Figure 2-8. Multiple Normally Closed Sensors
To wire several normally open sensors to one alert input,
connect them in parallel. To do this, take one lead from each
sensor and attach it to the numbered terminal. Then, take the
second lead from each sensor and attach each to the corre-
sponding ground screw. Refer to Figure 2-9.