Add safety and convenience to your home, cottage or business. When linked to an Ideal automatic telephone dialer the SK640 will notify you by telephone of a power failure and trigger a 30 second built in alarm (BiBiBi). When plugged into a 110 volt outlet, a blackout, power failure or circuit interruption, will trigger the included batteries to power the unit to send a signal to a dialer, an alert or an Ideal wireless siren. A land telephone line is required for the calling feature. The SK640 is designed to be left plugged into an outlet at all times. The SK640 includes the sensor; a UL approved adapter, 3 AAA batteries, instructions and wall mounting screws. The low battery LED will flash and a “di-di” sound will be heard to remind you to change batteries to ensure continued service. The sensor can be used with the alarm sound or in silent mode. The wireless signal will be sent in either mode.