Add-on accessory sensor for Lyric Wi-Fi Leak and Freeze Detector (RCH3610WF1001/N sold separately). Must be connected to base unit RCH3610WF1001/N to activate sensor</br>This 4 foot add-on Rope Sensor can be linked with multiple Rope Sensors to extend the detection area of the base unit (RCH3610WF1001/N sold separately) up to 500 feet.</br>When used with the base unit (RCH3610WF1001/N sold separately)