ANORDNING FOR DETEKTERING AV INTRENGANDE FOREMAL ELLER PARTIKLAR

摘要

The disclosure relates to devices to detect intrusion of a small mass into a doorway or the like. Detection is caused by interruption of a rapidly scanning or other appropriate light beam or radiation source which impinges upon a photovoltaic or photoconductive tape fastened to the perimeter of the doorway. Interruption of the light beam or its equivalent causes a momentary reduction in current or voltage emitted by the tape.