polarity insensitive connection

SIL3 safety integrity level direct from Wanlin Fire Protection — 12-year factory experience, WL-SFP800 smart fire detector certified CE/EN14604/EN54/UL217/UL268/FCC. Key specs: Photoelectric Smoke Sensing + RF Wireless Interconnect (433MHz/868MHz) + Mesh Network + Self-Healing Topology, RF Wireless Mesh + 4G LTE Cat.1 Gateway + Cloud Platform + SMS/Push/Emai···