Model WSG - Wireless Humidity Sensor
From Wireless Sensors
The WSG Wireless Humidity Sensor is designed to work exclusively with the Sensaphone WSG30. This sensor includes a built-in radio transmitter and humidity sensor element for monitoring humidity wherever the device is installed. The sensor comes with two AA alkaline batteries which will power the sensor for up to two years. An optional plug-in power supply is also available. The batteries then become a backup if main AC power fails.