The ultrasonic movement detector was designed for small residential security systems. Because of lack of the right housing, the injection molded form was designed under original Elbox's cover project.
Most of this sensors, produced in the years 1990-1994 are still working.

FIG. 1
Ultrasonic Movement Detector - a black part is the cover foam. Because it should be transparent for ultrasonic waves it took some time to find the proper material.

FIG. 2

Inside view of this detector. The version on a picture is equipped with some useful functions: movement test, sensitivity and a range switch and a interference level monitor with a memory.

FIG. 3
This sensor was well characterized - here, the ultrasonic radiation pattern.

FIG. 4
An element side. Two transducers, two LED's and other elements.