Magnetic article surveillance system and method

摘要: A surveillance system based upon generation and detection of phase shifted harmonic signals from markers on articles or persons, responsive to transmission a reference signal at fundamental frequency in zone, may be adversely affected by the presence zone large metal objects, such as shopping carts. Such objects can alter predetermined values. An alternate processing technique for recognizes that immunity disturbances achieved measuring between two more returned marker, because effect has been found have same all signals. Correspondence difference is reliable indicator marker detection.