PHASE METHOD OF DETECTING UNAUTHORISED CONNECTION TO TELEPHONE LINES Russian patent published in 2011 - IPC H04M1/68 H04L12/22 G01R25/00 

FIELD: information technology.

SUBSTANCE: to detect a device connected to a telephone line for unauthorised information tapping, values of phase shift between the input and output voltage of a bridge measuring circuit are measured using a phase-measuring device. Presence of devices connected to the telephone line for unauthorised information tapping is determined from results of comparing values of deviation of the measured phase shift from the standard value.

EFFECT: high sensitivity and reduced error of results for monitoring the wire electrical channel of a telephone line for presence of unauthorised information tapping devices connected to the telephone line.

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