|Device Type:||SMOKE DETECTOR|
|Power:||12 OR 24 VDC|
|UL Listed:||UL LISTED|
These smoke detector heads are a part of two component modular detectors, the second component being the detector base. A variety of bases are compatible with these heads, with applications for two- and four-wire circuits operating in 12 or 24 V systems. The bases are permanently attached and wired to backboxes. The interchangeable heads quickly detach for replacement and cleaning without disturbing the circuit wiring. Head removal results in a trouble signal at the panel. The Bosch D285 Photoelectric Smoke Detector Head uses an infrared LED light source and a silicon photo diode to measure light in a chamber. In normal conditions the light source is absorbed in the chamber. The presence of a significant number of particulates allows the light to reflect to the photo diode. Diode measurements exceeding the alarm threshold cause the unit to signal an alarm condition. The detection chamber, designed for reliable smoke entry characteristics, is protected by a micro-fine insect screen to reduce dust accumulation and minimize nuisance alarms. To further reduce nuisance alarms, the D285 and D285TH heads check their calibration. This Chamber Check feature is automatic. If the head is out of calibration for a period exceeding 24 hours, the Trouble/Alarm LED flashes once per second, three times the normal rate.
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