Dynamic convergence circuits for multiple gun cathode ray tubes

Claim 1

IN A SCANNING CIRCUIT FOR A COLOUR TELEVISION RECEIVER, INCLUDING A THREE GUN CATHODE RAY TUBE FOR DISPLAYING COLOURED IMAGES AND MEANS FOR DEFLECTING THE BEAMS FROM SAID GUNS IN LINE AND FIELD DIRECTIONS TO DESCRIBE A TELEVISION RASTER; AN ARRANGEMENT TENDING TO PRODUCE DYNAMIC CONVERGENCE OF THE BEAMS OF SAID TUBE, COMPRISING (A) ELETROMAGNETIC MEANS ASSOCIATED WITH EACH GUN WHICH WHEN ENERGISED WITH CONVERGENCE CURRENTS OF LINE OR FIELD FREQUENCY SET UP MAGNETIC FIELD CAUSING CONVERGENCE DISPLACEMENT OF THE BEAMS FROM SAID GUNS, (B) TERMINAL MEANS FOR SUPPLYING SAWTOOTH CURRENTS OF ONE OF EITHER FIELD FREQUENCY OR LINE FREQUENCY, (C) TERMINAL MEANS FOR SUPPLYING PARABOLIC CURRENTS OF THE SAME FREQUENCY AS THE SAWTOOTH CURRENTS, (D) AT LEAST ONE COMBINING MEANS FOR COMBINING SAID SAWTOOTH AND PARABOLIC CURRENTS, (E) MEANS FOR APPLYING SAID COMBINED CURRENTS TO EACH OF SAID ELECTROMAGNETIC MEANS, (F) ADJUSTING MEANS ASSOCIATED WITH SAID ELECTROMAGNETIC MEANS FOR ADJUSTING THE AMPLITUDES OF CURRENT THEREIN, (G) AND A SINGLE MEANS FOR ADJUSTING THE RELATIVE AMPLITUDES OF THE SAWTOOTH AND PARABOLIC CURRENTS APPLIED TO SAID ADDING MEANS.