Cathode ray tube apparatus
OwnerElaine Chase, Adrian M. Clitheroe +2inventors
InventorsElaine Chase, Adrian M. Clitheroe, Edward T. Shepherd, Peter Beanlands
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Abstract
Cathode ray tube apparatus including compensation (14) for the vertical component of terrestrial and of other ambient magnetic fields (15). The compensation is achieved by the generation of an opposing vertical magnetic field by energization of the degauss coil (11, 12) in the apparatus. Two embodiments are described: one applies a continuous direct current (21) after the degaussing operation and the other applies a direct current component coincident with the degaussing signal to permanently magnetize components of the apparatus. The magnitude and polarity of the compensation provided may be variable.
Claims10
A cathode ray tube apparatus including a cathode ray tube (10) with a degauss coil (11, 12) for reducing magnetization of the apparatus and circuitry (13) coupled to the degauss coil, in which the degauss coil is positioned, constructed and arranged and said circuitry (13) produces a signal that drives said coil having a decaying time varying component and a non-zero dc component to produce residual magnetism (14) in opposition to the vertical component of the terrestrial and other ambient magnetic fields (15), thereby to produce a resultant vertical component of the magnetic field (16) in the region of the cathode ray tube of lower amplitude than said vertical component of the terrestrial and other ambient magnetic fields (15).
Dependencies are inferred from the claim text.