Acoustic and visual alarms usually work through an electronic circuit. When the alarm is triggered, the circuit causes a buzzer to sound and simultaneously controls a flashing light. The circuit will also control a switch that is used to activate and deactivate the alarm. Typically, an alarm will have a sensor that detects changes in the surrounding environment and triggers the alarm when a specific event occurs. For example, an audible and visual alarm might be used in a burglar alarm system, where the sensor triggers the alarm when someone comes within detection range.
Audio-visual alarms are typically used for alerts and warnings, and common uses include: anti-theft systems, fire alarms, medical equipment, industrial equipment, and vehicle safety equipment.