FIELD: industrial and commercial anti-espionage methods for preventing listening to remote secret negotiations carried out indoors.
SUBSTANCE: proposed method for preventing modulation of laser beam by window glass directed thereto with aid of voice signals and demodulation of return beam includes detection of window opening angle affording pick-off of acoustic information, photographing of space adjacent to window at minimum three points of window, and recording of vertical and horizontal displacements of camera in the course of shooting. Then typical objects of space under investigation are selected on one of photographs obtained, selected objects are aligned with similar objects on other photographs, and amounts of horizontal and vertical shifts of photographs required for alignment are measured. Results obtained in measuring camera displacements and photograph shifts are used to calculate distance from window to typical objects. Finally window opening angle is projected on photograph of selected typical objects and potentially risky zone of listening is evaluated by calculated distances to typical objects covered by opening angle.
EFFECT: enhanced effectiveness of protection against unwanted listening.
5 cl
