Microwave sensors are great for convertible vehicles as the alarm can be armed with the top down. They are also good for situations where car windows are left open while the alarm is armed.
A microwave sensor picks up physical movement or body mass movement (rather than air movement like an ultrasonic sensor). Within the sensor is a microwave generator that creates a mushroom shaped field around the sensor.
This model is a single zone microwave which detects movement within the car. For example in a convertible if anyone climbs over the doors the sensor will detect the movement and trigger the alarm.
It can be added as an optional upgrade to any 12 volt AVS car alarm.
A dual zone microwave is also available.