METHOD FOR CONCEALED SUPPRESSION OF EAVESDROPPING DEVICE, CONTAINING A MICROPHONE AMPLIFIER Russian patent published in 2007 - IPC H04K3/00 

FIELD: radio engineering.

SUBSTANCE: in accordance to concealed eavesdropping device suppression method, which device contains microphone amplifier, ultrasound is generated in form of bi-harmonic oscillation, frequencies f₁ and f₂ of which are selected from condition of occurrence of combination frequency f₃ in spectral range of speech, equal to |2f₁-f₂|, if f₂>f₁, and |2f₂-f₁| if f₂<f₁, one of frequencies f_1,2 or both frequencies are altered chaotically so that frequency f₃ changes chaotically within limits of spectral range of speech, generated ultrasound oscillation is emitted in direction of eavesdropping device, in microphone amplifier of which modulation interference occurs, overlapping spectrum of speech signal.

EFFECT: increased range of suppression of eavesdropping device due to usage of energetically efficient principle of interference generation on basis of deliberately caused inter-modulation distortions of third order.

2 cl, 6 dwg