This wireless driveway alarm is the perfect system for monitoring two entrances from two locatons! This dual kit comes with two driveway sensor transmitters and two wireless receiver chimes. Each of the two transmitters operates off of a 9 volt transistor battery. The receiver chimes plug into an ordinary electrical outlet and feature built-in volume control. Each of the transmitters can be set to play a specific notification/tune. This means that each of the driveways being monitored can have a different sound!