Smoke Alarm, Detection Method Photoelectric, No Interconnection Capability, Power Source 12/24 VDC, Four-Wire, Visual Alert Red LED, Diameter 5-19/64 In., Height 2 In., Digital Readout No, Battery Backup No, Features Removable Detector Cover and Chamber, Built-In Remote Maintenance Signaling, Drift Compensation and Smoothing Algorithms, Thermal Sensor, Hush Button No, Locking Pin No, Operating Temp. 32 Degrees to 120 Degrees F, Standards UL, CSFM, Includes Base