1. independent smoke sensor 2. dampproof, dustproof, mothproof 2. anti extraneous ... structure7. Dustproof, insect prevention and anti extraneous light interference8. Independent smoke sensor. Technical Parameter:ModelWL-258DWorking voltage9VDCsensorOptical mazeworking currentStatic current ... % per FeetWorking environment-10°C~+50°CVolume85dBDimensionΦ106*36mm Independent Photoelectric Smoke Sensor