METHOD AND DEVICE FOR DETECTING UNATHORIZED ACCESS TO OBJECT UNDER QUARD Russian patent published in 1996 - IPC

FIELD: guard of metal articles. SUBSTANCE: speed of change gradient of electrostatic field is measured at area action of aerials to fix action on objects under guard. Signal received from area of action enters amplifier with controlled gain through differentiating circuit and lower frequency filter (intergrating circuit is brought into filter circuit). Then signal enters actuating unit which begins to operate when signal reaches threshold value. Galvatic decoupling in differentiating unit and amplifier eliminates influence of inducing surface currents and allows to generate artificial electrostatic field. EFFECT: improved noise immunity; improved operational capabilities and sensitivity. 3 cl, 1 dwg