Abstract: An electrical invertor circuit comprising a first common electrode and at least two secondary electrodes and means permitting an electric discharge to be established between said first electrode and any one of said second electrodes. A magnetic field is applied through the gaps between said first electrode and said secondary electrodes so as to switch the discharge from one to another of the secondary electrodes. In one arrangement there are two secondary electrodes in the form of two secondary substantially semi-annular electrodes disposed around a circular central electrode so that a rotating spoke discharge is formed. The two semi-annular electrodes are then connected to the terminals of the primary winding of an output transformer whereas a center tap of said winding is connectable to the central electrode through a D.C. power supply.