The GE Deluxe Door Alarm simply attaches to your door, with a magnetic sensor going on the frame next to it. The alarm can be set to HOME or AWAY mode: in HOME mode, an alarm sounds immediately when the door is opened; in AWAY mode, there is a 45-second delay to allow time to enter your 4-digit code to disarm the system. The 4-digit code can be set or changed by the user. In addition to the alarm, the system can be set to play a chime with the door opens, making it perfect for any entrance! Requires 3 AAA batteries (not included). Operating gap between alarm and magnet is a maximum 1/2 inch.