One potential component of a full-spectrum home security system is a driveway alarm, useful for instantly alerting you to the movement of a vehicle and/or person onto or off of your property. Similarly, a driveway alarm is often installed as a standalone unit for the same purpose. Most driveway alarms are wireless units featuring an outdoor sensor and transmitter along with an indoor receiver. Wired units are available, however, but are limited to metal motion probes for detecting vehicle traffic. Wireless units typically feature an infrared sensor that can accurately detect human movement as well as vehicles, but other sensor types are employed as well.
Infrared or PIR sensors are very effective at detecting the movement of vehicles, people or large animals at a distance of up to 80 feet from the sensor location. Infrared driveway alarms are wireless. Once movement is detected, the sensor/transmitter signals the indoor receiver where a chime, tone or some other form of notification sounds.
Metal Probe Sensors
Metal probe sensors are actually hybrid units, incorporating both wireless and wired technologies. Parallel to a driveway, the metal probe is buried. Attached to a wire, it connects to the transmitter located up to 50 feet away. The probe detects metal at a variable distance, at which point the transmitters sends a signal to the indoor receiver, similar to the infrared sensor.
Rubber/Air Hose Sensors
A third type of driveway alarm involves a pressurized rubber air hose. This alarm, too, combines wireless and wired aspects. Extend the hose across a driveway. The weight of a vehicle forces compressed air into a sensor in the transmitter, which then signals the receiver and notifies the occupant of the home.
Home driveway alarms range in price from around $100 to $200 or more, depending on the brand, transmission range and alarm type. Whichever alarm works best for your driveway, you will always know when a vehicle, or in some cases people too, cross the threshold onto your property.