UFC 4-021-02NF
27 September 2006
change 1, 23 October 2006
the acoustic sensors are disabled. When the building is secured and unoccupied, the
acoustic sensors are activated. After hours intruders make noise which is picked up by
the acoustic array and an alarm signal is generated.
5-3.6.1
Acoustic sensors act as a detection means for stay-behind covert intruders.
5-3.7
volumetric intrusion detection sensors. PIRs pickup heat signatures (infrared emissions)
from intruders by comparing infrared receptions to typical background infrared levels.
Typically, activation differentials are 3 degrees Fahrenheit. These devices work best in
a stable environmentally-controlled space.
5-3.7.1 Different cones or cowlings can be placed on the PIR to focus or spread-out
the coverage of the detection window. In other words, standard supplied covers for lens
can be made to provide a more narrow or wider sensor coverage area.
5-3.7.2 While not a security application, PIRs are often used as an automatic request
to exit device for magnetically locked doors. In this application, the PIR acts as the
automatic sensor for detecting an approaching person in the exit direction for
magnetically locked doors.
5-3.7.3
PIR Sensor Guidance:
5-3.7.4 Do not use near exterior doors where the sensor can be exposed to sudden
changes in background environmental temperature.
5-3.7.5
Best use is in interior climate-controlled spaces.
5-3.7.6 PIRs can receive false alarms from other heat radiating objects such as heat-
system registers, rodents, pets, or other warm objects (in one case a mop bucket with
hot water in it).
5-3.7.7 PIRs can also be defeated by a trained, slow-moving intruder. (Very hard to
achieve.)
5-3.7.8 PIRs are much more sensitive to travel crossing its sensing area as opposed
to travel toward the sensor.
5-3.8
Ultrasonic Sensors use active transmission of sound waves to pick up
intruders much like a radar transmitter and receiver. To get an alarm signal, a signal
must be transmitted, bounced off an intruder and receipt signal received. Ultrasonic
sensors are rarely used.
5-3.9
within one housing. An alarm condition is generated if either the microwave or PIR
sensor detects an intruder. In some dual-technology sensors, alarm settings may be
adjusted to require that both the microwave and the PIR unit detect an intruder
presence before an alarm condition is generated. Since two independent means of
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