an improved circuit for suppressing the occurrence of a sharply - focused light spot on the screen of a television receiver when the set is turned off is described . a normally conductive , controllable electronic switch is normally effective to maintain the brightness control grid of the cathode ray tube blocked , such switch assuming its non - conductive state only during the presence of the normal forward sweep portion of the deflection voltage to impart a positive step in voltage to the control grid to permit the now - moving light spot to be visible on the screen . during the flyback portion of the deflection voltage , or equivalently during the disabling of the tv set so that no forward sweep voltage is present , the controllable switch reverts to its &# 34 ; fail - safe &# 34 ; conductive condition to immediately restore the negative blocking voltage on the control grid to inhibit the beam current and thereby the formation of the now - stationary light spot .