The remote indoor temperature sensor is used to sense temperature remotely. It’s a wireless indoor air sensor and isRedLINK™ enabled. It can be used to sense temperature if the thermostat is installed in a poor temperature sensing location. It’s easy to install and use. Mounting: Mounts on a vertical wall with supplied bracket and mounting hardware,Operating Humidity Range (% RH): 5 to 90% RH, non-condensing,Operating Temperature Range (F): 35 F to 114 F for optimal battery life,0 F to 120 F,Operating Temperature Range (C): -17.8 C to 48.9 C,1.7 C to 45.6 C for optimal battery life