the invention relates to a deflectional system of a television set comprising a power transistor and a driving circuit which supplies a deflection current increasing in ramp - shaped manner to a deflection coil . the driving circuit is periodically fed with switching - on pulses of a duration corresponding to the ramp length of the deflecting current . the driving circuit applies an increasing switched - on base current to the power transistor during the switching - on pulse duration , said switched - on base current driving the power transistor into the saturation state during substantially the entire switching - on pulse duration . after termination of the switching - on pulse , the driving circuit controls the power transistor with a switching - off base current which rapidly decreases in relation to the increase of the switched - on base current and finally changes polarity and which effects a rapid return of the power transistor from the saturation state into the blocking state . the power transistor has a sensor means associated therewith which supplies to the driving circuit an actual - value signal which is proportional to the instantaneous value of the transistor main current . the driving circuit regulates the switched - on base current , during the entire increase thereof and in accordance with said actual - value signal , to a value which maintains the power transistor in the saturated stated with only a slight degree of saturation . the driving circuit controls the steepness of the switching - off base current proportionally to the actual - value signal occurring at the end of the switching - on pulse .