From outside, it sounds like you have a very unfriendly dog inside. It also can announce visitors with a chime or alarm. The radar sensitivity is adjustable from 10-20 feet. Volume is also adjustable. Dimensions 6" x 7" x 4 3/4". Powered by AC power supply. Also takes 8 AA back-up batteries (not included) in case of power loss. Unit needs to face in the direction you want to detect motion. Detection is limited from the sides and rear. The included remote control lets you Arm and Disarm the system, as well as set off a Panic alarm. You can also connect one additional sensor (HA-MOTION or HA-SENSOR).