Degaussing device for a color television display tube

Claim 1

A color cathode ray tube having an evacuated envelope including a neck portion, a truncated conical front portion and deflection means located at the junction of said neck and front portions and, within said envelope, means to generate a number of electron beams emanating in a substantially horizontal plane during the normal operating condition of the tube, a color selection electrode made of a ferromagnetic material and provided with a plurality of slots, a display screen at the wide end of said front portion, said screen having a plurality of phosphor stripes, said slots and said stripes being arranged according to a pattern of lines which extend substantially vertically during the normal operating condition of the tube, a degaussing device comprising a shield of ferromagnetic material disposed substantially parallel to the conical wall of said front portion, at least one degaussing coil embracing a major surface portion of said conical wall and oriented such as to provide, when energized by an alternating degaussing current, a substantially vertically directed magnetic field in said color selection electrode, and shunting means connected parallel to said degaussing coil and having an impedance which is higher than that of said degaussing coil at the frequency of the degaussing current but lower at the frequency of the line deflection current.