Never miss an important visitor or package delivery again with the Reporter Wireless Driveway Alert System that detects and reports people or vehicles and reports the results to a receiver unit inside the house. Just place the sensor near any location needing notification or protection including driveways, business entrances, garages, and barns and when it detects activity, the receiver unit inside the house will sound a tone. It's ideal for monitoring boats, RVs, trucks, mailboxes or anything else you can think of. Four AA batteries (sold separately) will power the unit for approximately 2 years. The expandable Driveway Alert security system comes with one sensor and one receiver. Up to three additional transmitters (each sold separately) may be added to each receiver, allowing you to cover four different locations simultaneously, each with four distinct beeps. Other features of the Reporter Wireless Driveway Alert System include: # Amazing range; the sensor has a 30' range and can transmit a signal to the receiver up to 1,200' away # Detects humans and vehicles, but ignores animals # Waterproof sensor assembly # Weather shield included to protect sensor from the elements # Receiver features sound control and has an output to trigger external alarms or bells # Microprocessor code-learning technology eliminates false alarms receiver responds only to transmitters assigned to it