The SignaLink™ Bridge WIRLESS SUPERVISORY SYSTEM can monitor any dry-contact switch (not listed as explosion proof) and transmit their status wirelessly to any fire alarm panel. It uses a wireless transmitter and wireless receiver to fully monitor the switch's state and operates on 2.4 Ghz. The enclosures are constructed of weather and UV resistant polycarbonate with a NEMA 4 rating of -40° F to 120° F. UL listed.