Control Products WS-04 WaterSiren Plus 90 decibel alarm provides quick alert if you're home. Plug into the Deluxe FreezeAlarm (FA-D or FA-D2) and the WA-20 will trigger the FreezeAlarm to call any three phone numbers to warn of a water emergency. Detachable water sensor can be placed on floor, inside the lip of a sump, near a water heater, washing tub or machine, or near any plumbing fixture. Operates on a 9V alkaline battery (not included). Sounds an audible alarm for up to 36 hours on a fully charged 9V battery.