Dwyer Instruments” Series WTP wireless temperature sensors can be installed on chilled water lines, air ducts or outside a building without having to run additional wiring. By sampling the temperature measurement every 10 seconds, the 3.6V lithium battery is able to power the unit for up to eight years. A 418 MHz signal can carry the measurements up to 100 feet without a repeater. With the optional 900 MHz repeater, measurements can be transmitted up to 1000 feet away.