Rex Plus II, the electronic watchdog alarm, is versatile and provides an excellent way to deter burglars, without the responsibility of owning a real dog. With his electronic radar eyes, Rex II can “see” through thick doors, walls and glass. When movement is detected, he starts to emit sound (select from two barking sounds). The closer an intruder gets, the more frequent the barking becomes. As the intruder backs off, the barking decreases in frequency, stopping completely when movement is out of range. Rex II also offers a siren or a pleasant greeting.