Shock
Feels impacts and vibration. It is the basic sensor, and most alarms include one. It is usually adjustable.
Glass break
Listens for the particular sound of breaking glass, which is useful because a window can be broken with very little shock.
Tilt
Notices when the car is raised or tilted, as with towing or wheel theft.
Cabin and field disturbance
Watch the inside of the car for movement or disturbance, useful for convertibles, soft tops and vehicles with open cargo areas.
Putting them together
More sensors mean more coverage, but also more tuning. A good installer sets each sensor to a level that does not cry wolf.
Matching sensors to parking
Street parking: shock, glass-break and tilt. Apartment lot: the same, plus a loud siren. Home garage: shock and a starter interrupt. Trailhead or lake lot: add a cabin sensor. Convertible or soft top: cabin or field sensing is the one that matters.
Quick answers
Which sensor should I add first?
For most vehicles, a glass-break sensor is a smart second layer.
Do sensors drain the battery?
Very little when properly installed.
