35 feet] [as indicated]. Sensor shall not alarm in response to
general area thermal variations.
b.
Dual technology sensors: Provide sensor combining passive
infrared and microwave sensors designed and manufactured
specifically to be mounted in a single enclosure.
(1) Passive infrared (PIR) sensor section: Sensor shall detect
intruder presence by monitoring the level of infrared energy
emitted by objects within a protected zone. Sensor shall initiate
an alarm upon observing increased or fluctuating infrared energy
caused by the presence and motion of an intruder whose temperature
is as little as 1.5 degrees C 3 degrees F different from the
background temperature. Sensor shall be passive in nature; no
transmitting energy shall be required for detection. Sensor shall
be sensitive to infrared energy emitted at wavelengths
corresponding to human body or other objects at ambient
temperatures. Sensor detection pattern shall be 3.14 rad 180
degrees for volumetric units, unless otherwise indicated.
(2) Microwave sensor section: Sensor shall detect intruder
presence by transmitting electromagnetic energy into a protected
zone, receiving the direct and reflected energy, and monitoring
the frequency shift between transmitted and received signals. If
more than one device is used in an area, devices shall operate on
different frequencies. Provide for selective filtering by sensor
to minimize nuisance alarms due to moving metal objects such as
fan blades and venetian blinds, interference from radar, or other
sources of electronic interference. Transceivers shall consist of
a combined transmit/receive antenna and an adjustable-gain
preamplifier in a single housing. Provide transceivers with
sensitivity adjustments. Transceiver controls shall permit
adjustment of transmission range and alarm signal threshold.
Sensitivity controls shall be inaccessible to operating personnel.
Sensitivity requirements shall be met with sensitivity controls
set approximately at midrange.
(3) Additional dual technology sensor requirements: Enclosure
containing the two sensor sections shall be tamper alarmed. Both
the microwave and PIR sections shall activate simultaneously to
generate an alarm. Only an intrusion characterized by volumetric
motion and radiant body heat shall be detected. Sensor shall
provide a means of indicating an alarm condition during
installation and calibration. A means of disabling the indication
shall be provided within the sensor enclosure. Sensor shall alarm
when an intruder moves within the area of protection more than
1500 mm 5 feetat a velocity of 30 mm 0.1 foot per second, and one
step per second, assuming 150 mm 6 inches per step.
Detection sensitivity shall be irrespective of direction of
motion. Sensor shall also alarm at velocities faster than 30 mm
0.1 foot per second, up to 3000 mm 10 feet per second. Sensor
shall not alarm in response to general area thermal variations.
Mount sensors [near ceiling on vibration-free surfaces] [as
indicated]. Electronic circuitry shall be solid state and mounted
on printed circuit boards. Sensor elements shall contain
circuitry for transmitter drive, signal processing, tamper
circuitry, and power supplies. Circuitry shall provide an alarm
relay with Form C contacts capable of carrying 2 amperes at 100
volts dc minimum.
SECTION 13703N
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