Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1989-06-30
1990-11-06
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
335219, 335284, 335302, 340572, G08B 1324
Patent
active
049689720
ABSTRACT:
A method of deactivating a frequency-dividing-transponder that includes an active strip of magnetic material that, when magnetically biased to be within a predetermined magnetic field intensity range, responds to excitation by electromagnetic radiation of a first predetermined frequency by radiating electromagnetic radiation of a second predetermined frequency that is a frequency-divided quotient of the first predetermined frequency; and a magnetized bias strip of magnetic material having first and second ends and disposed in relation to the active strip of magnetic material for magnetically biasing the active strip of magnetic material to be within the predetermined magnetic field intensity range only when the bias strip of magnetic material is magnetized includes the step of converting the bias strip of magnetic material into a tripole bar magnet, having a pole of one magnetic polarity in a predetermined region of the strip located between the ends of the strip, and having a pole of a different magnetic polarity than the one magnetic polarity at each end of the bias strip to thereby provide opposing magnetic bias fields in opposite longitudinal halves of the active strip for causing any electromagnetic radiation of the second predetermined frequency that is generated in one half of the active strip to be of equal and opposite polarity and thus cancelled by any electromagnetic radiation of the second predetermined frequency that is generated in the other half of the active strip. This is accomplished by laterally passing a magnet across and in close proximity to the bias strip of magnetic material, with the magnet having sufficient flux density to overcome the magnetic bias of the bias strip, and with the magnet being passed across the predetermined region of the bias strip.
REFERENCES:
patent: 3781661 (1973-12-01), Trikilis
patent: 4158434 (1979-06-01), Peterson
patent: 4727360 (1988-02-01), Ferguson et al.
Callan Edward W.
Security Tag Systems, Inc.
Swann III Glen R.
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