Check the listing for details. Simplex 4098-9602 TrueAlarm Photoelectric Detector. Condition: New. Listed at 68.99 USD. The Simplex 4098‑9602 TrueAlarm Photoelectric Detector integrates a high-performance photoelectric smoke sensor with a fast-response thermistor-based heat module, providing comprehensive multi-mode fire detection. Utilizing patented TrueAlarm sensitivity drift compensation, it continuously adjusts to environmental changes—dust, dirt, and aging—to maintain reliable smoke monitoring. The onboard heat sensor includes both fixed-temperature (135 °F/57 °C) and rate-of-rise (>20 °F/min when ambient ≥90 °F) detection. The TrueSense algorithm correlates smoke and thermal activity for intelligent, earlier fire response while minimizing false alarms. Mounting to a standard 4098 series base, the unit supports both 2-wire and 4-wire configurations, offers magnetic testing via LED indication, and is.