Apesto (The Sentry) Safety Technology International Electronic Watchdog, Barking dog, chime & alarm mode. Window, Door & Wall motion detector radar sensor with adaptor or wireless battery. Protection: The Sentry gives you and your family members a peace of mind, operates 24 hours a day and 7 days a week. It will standby to alert you to movements outside your house without stepping out of the house. Mode: Comes with 3 different settings ( Aggressive Dog Barking, Alarm Siren & Chime ). It comes with adjustable volume and sensitivity control knob, to adjust the the device to your preference. Power Supply: It can powered with the provided adaptor or for more portability it can also be powered by batteries. Features: The unit is water resistant, loud wide range speaker to provide the amplification deep bark sound of the dog, light & portable and very easy to set up with zero maintenance Technology: The Apesto Sentry uses special radar frequency waves that can detect movements behind solid objects such as walls, doors and windows. The waves are safe to be around much like radio waves it is not harmful to humans or pets.