449CT Smoke Detector (Self-Diagnostic, Photoelectric, 4-Wire with Heat Sensor) The 400 Series self-diagnostic, 4 wire smoke detectors continually monitor their own sensitivity and operational status, and provide a visual trouble indication if they drift out of sensitivity range or fail internal diagnostics. This meets NFPA 72 field sensitivity testing requirements without the need for external meters. Additional diagnostic information is activated by applying a magnet near the detector"s integral reed switch. This initiates a self-diagnostic routine and provides visual indication of sensitivity level, or if service is required. The 400 Series is easily cleaned by simply replacing ESL"s proprietary field-replaceable optical chamber (part 211). All models are designed to reduce false alarms from dust, insects, RFI and external light. An integral combination rate-of-rise and fixed 135degreesF (57degreesC), 50-foot rated, heat sensor is available with all T model detectors (see selection guide). An integrated silicon heat sensor and a dedicated microprocessor are used to detect heat and perform the rate of rise calculations, for earlier heat detection. Models with auxiliary relays are approved for releasing service. The very low profile 400 Series detectors are equipped with a hinged cover, a concealed tamper-resistant latch, and insect screens.