A door protected with a contact cannot be opened more than ____ without initiating an alarm.

A door protected with a contact cannot be opened more than ____ without initiating an alarm.

• A. 4 inches
• B. 1 inch
• C. 2 inches
• D. 6 inches

Answer: (C)

A door with a contact uses a magnetic switch that stays closed when the door is shut. When the door is opened and the gap between the door and frame grows beyond the designed limit, the switch is activated and the alarm is triggered. The specified limit of two inches is chosen because it’s small enough to detect forced entry attempts but large enough to avoid false alarms from normal door movement or minor misalignment. If the door is opened more than two inches, the alarm should fire; if it were set smaller, everyday movement could cause false alarms, and if it were set larger, a burglar could open the door farther without triggering.

A door with a contact uses a magnetic switch that stays closed when the door is shut. When the door is opened and the gap between the door and frame grows beyond the designed limit, the switch is activated and the alarm is triggered. The specified limit of two inches is chosen because it’s small enough to detect forced entry attempts but large enough to avoid false alarms from normal door movement or minor misalignment. If the door is opened more than two inches, the alarm should fire; if it were set smaller, everyday movement could cause false alarms, and if it were set larger, a burglar could open the door farther without triggering.