Antirobo alarm apparatus. (Machine-translation by Google Translate, not legally binding)

摘要

Anti-theft alarm device, characterized in that it consists of a generating and ultrasonic emitting device mounted inside the enclosure to be controlled, and an ultrasonic receiver device mounted at a point of said enclosure so that it responds to the field strength constant ultrasonic, present at said point, to give an electric magnitude of equally constant characteristics, and means that respond to a variation of said electrical characteristics, corresponding to an alteration of said field strength, to determine the operation of an indicating device or alarm. (Machine-translation by Google Translate, not legally binding)