Abstract: A mode discriminator for detecting a specific mode of horizontal synchronizing frequency applied to a display monitor includes first and second monostable multivibrators coupled to a vertical synchronizing signal associated with the horizontal synchronizing frequency. The discriminator detects the polarity of the vertical synchronizing signal to detemine whether the horizontal synchronizing frequency is of a first mode or a second mode in which the frequencies are different. Since the discriminator detects the polarity of vertical synchronizing signals and does not depend on the time difference between pulse widths of a horizontal synchronizing signal, reliability and performance are enhanced.

Abstract: A high voltage stabilization curcuit for a multi-frequency horizontal deflection circuit in a video monitor or receiver and having a plurality of supply voltages applied to the flyback transformer of the deflection circuit through the operation of a pair of series connected switching circuits whereby different amplitude power supply voltages are coupled to the primary winding of the flyback transformer depending upon the horizontal drive frequency being utilized. The high voltage output across the secondary winding of the flyback transformer is stabilized through a feedback circuit which senses the output across the secondary winding of the flyback transformer to increase the amplitude of the horizontal drive applied to the primary winding when the high voltage output across the secondary winding decreases by means of a boost circuit coupled to the horizontal output circuit coupled to the primary winding.