They tied up a cashier and a security guard minutes before the guard was due to activate the alarm system.

Fire alarms and other emergency switches are typically non-reversible, using a piece of glass which must be broken to activate the alarm.

U-boat order to activate the alarm and begin a crash dive.

Once detected, an electronic signal can activate an alarm or a camera that can capture an image or video of the motioner.

The signal locks or unlocks the doors and in some cases activates an alarm.