Bosch Photoelectric Beam, DS422i

The DS422i and DS426i are dual-beam photoelectric detectors designed for indoor and outdoor applications. Consisting of a separate transmitter and receiver, they are designed to activate an alarm when an intruder passes within the direct line of sight between the transmitter and receiver. The D422i has a range of 30 m (100 ft) outdoors or 90 m (300 ft) indoors.
Dual beam detection
Range up to 60 m (200 ft) outdoors, 180 m (600 ft) indoors
Selectable response time
Small unobtrusive design