The signal in an ultrasonic detector can identify the speed of the object, the direction of movement, the distance the object has moved, the distance between object and detector, and the number of changes in direction. The signal of a passive infrared detector depends on the temperature difference between target and ambient, wavelength of the IR, and angular target speed and distance. The MATCHTEC detector combines ultrasonic and passive infrared detection and has sufficient intelligence to compare what it sees with what it hears. The detector's logic processor looks at all the relevant criteria from both detection systems and judges the results as an entity. The detector keeps the nuisance alarm rate low by understanding when a certain signal is likely to have been sent by an intruder under specific circumstances.