This depends on the type of sensor the driveway alarm uses. There are four basic types of driveway alarm sensors:
- Passive Infrared Sensor (PIR):
These are the most common type. Passive infrared sensors are triggered when a combination of heat and movement are detected in the monitored zone. This means a car, truck, person, or any animal will trigger the sensor IF it passes through the monitored zone.
- Magnetometer Bases Sensor:
These sensors are designed to pick up automobiles only and they work when heavy metallic objects are detected in the monitored zone. The sensor typically has a probe that is buried just under the driveway or parallel to the driveway. When a car or truck drives through the zone, the probe detects the change in the magnetic field and triggers.
Do you remember the old gas stations that had a rubber hose stretched across the entrance? It would ring a bell as the car rolled over the hose.
This type of sensor is called a pneumatic sensor. When a heavy cars rolls over the hose, the change in air pressure inside the hose triggers the sensor.
- Break Beam Sensor:
These sensors work in a pair and when someone, or something passes between the pair of sensor, they detect that the beam between them was broken and are thus, triggered.