Driveway Patrol is an infrared sensor that alerts you when someone crosses its path. When placed across the driveway or on your porch, a pleasant chime will sound alerting you that someone has come onto your property. Driveway Patrols amazing wireless technology provides easy mobility: simply place the sensor by the front door, garage, mailbox, or anywhere else near your home and the unit will send a signal to its receiver (up to 400 feet away)! With Driveway Patrols motion activation, you will always know when someone is coming up to your house before they ring the doorbell! Driveway Patrol is weather resistant, installs easily with only a screwdriver, and only needs one 9 V and 3 C batteries (not included). The Driveway Patrol motion detector notifier unit may also be used with a D.C. 4.5 volt connector instead of batteries. The Signal should be installed at a height of 4 feet to avoid feedback interference errors from the ground.