The GE magnetic alarm /chime with keypad system utilizes magnetic sensor technology to protect homes, businesses, garages, sheds and more from break-ins or home invasions. The magnetic contact alarm/ chime will sound whenever a door is opened more than 0.5 inches. The door alarms gives you a 30 second entry delay and a 45 second exit delay. In addition to a 120 dB alarm it has a chime that can be used to let parents know if a child has gone outside or a store owner if a customer has entered their shop. It is easy to install- no wiring is required. Uses three (3) AA batteries (not included). The door alarm/ chime can also be powered by an optional AC/DC 4.5 volt adpater (not included). The main unit is 4 inches x 2 and 1/2 inches x 1 inch in size.