Abstract: Deflection system for a cathode-ray tube comprising a pair of vertical deflection coils and a pair of horizontal deflection coils, the two pairs being electrically insulated by a separator. The system also comprises auxiliary coils modulating the horizontal scan velocity. The support 9 for the auxiliary coils, made of plastic, comprises openings 32 placed under the location 30 of the said auxiliary coils so as to decrease the relative permittivity of the space between these coils and the neck of the tube, which tends to decrease the occurrence of electric arcs in the neck of the tube when switching it on.