sensor fault alarm smoke detector

UL217 smoke detector direct from Wanlin Fire Protection — 12-year factory experience, WL-SM603 4G standalone smoke detector certified CCCF/GB 20517-2006/CE/UL 217/EN 14604. Key specs: Dual Light Path Photoelectric + Thermistor Heat Sensor + 4G Cat.1 Communication, 4G LTE Cat.1 + Cloud Platform + Dual Detection (Smoke + Heat) + SMS/Push/Email. Dual light pat···