The Secure Dog barking dog alarm system uses an electronic radar wave sense control. This technology allows it to see through virtually any non-metallic barrier. Will not work through metal doors. When an intruder enters the 100 degree triangle of protection, it automatically starts barking like an angry dog. From outside it sounds like a very mean dog inside. It can also announce visitors with a chime or alarm. The radar sensitivity can be adjusted from 10-20 feet. Volume is also adjustable. It also can announce visitors with a melody of birds, frogs and waterfall sounds. These relaxing sounds can also be played whenever you want a soothing background sound. Four settings to choose from: Continual tranquil sounds of the rainforest, Alert sound of an angry and protective watchdog, Soothing rainforest sounds to alert you of a guest"s arrival and Alert sounds of both the angry watchdog and a warning siren. * Reliable 24-hour protection * No Installation required * Protection with none of the problems of owning a real dog. * Switches from the watchdog to the tranquil sounds of nature with the simple switch of a button. * Variable distance sensitivity (up to 21") as well as volume control. * Senses movement through walls, doors, and glass to alert you of a visitor"s arrival. * Size: 7.5" x 5" x 5.5" * Maintenance free.