Model Number: TX-3FS. Key Specifications/Special Features: It activates alarm when the sensing probe of the detector areimmersed in waterPower source: two AAA alkaline batteriesCurrent drain: 3.5uA at standby, 20mA at activationEstimated battery lifespan: five yearsTransmitter dimensions: 20 x 29 x 123.5mmTransmitter weight (without battery): about 34gWireless, radio link with LS-30 alarm panel