Which sensor detects breaking glass?

• A. Glass-break sensor
• B. Door/window contact
• C. PIR motion detector
• D. Smoke detector

Answer: (A)

When guarding windows, you want a sensor that targets the actual event of a window being broken. A glass-break sensor is designed to do just that by listening for the distinctive impulse and high-frequency vibration patterns produced when glass shatters (or by detecting the resulting vibration). Mounted near a window, it can trigger the alarm as soon as the breaking event occurs, even if someone doesn’t fully open or reach through the window.

In contrast, a door/window contact only detects opening or movement of the window frame itself—so if the glass is broken without the frame moving as expected, that sensor may not be triggered. A PIR motion detector looks for heat and movement of a person, not the glass-breaking event. A smoke detector is for detecting combustion byproducts and is unrelated to break-in events.