Cathode ray tube deflection circuit having display format selection

An apparatus for selectively changing the display on the screen of a cathode ray tube from a first format to a second format in response to a format control signal including a horizontal deflection circuit 10 having an inductance 16, 30 with a first inductive value resonated with a capacitor 37 to a first horizontal sweep frequency, means 26 for generating a horizontal drive signal 24 in response to the format selection signal for driving the horizontal deflection circuit 10, the horizontal deflection circuit 20 determining the horizontal size of the display, means 26, 40, 42, 44, responsive to the control signal 27, for changing the inductive value of said inductance 16, 30 to a second value and thus changing the resonant frequency of the horizontal deflection circuit to a second value, means 26 responsive to the control signal 27, for changing the frequency of said horizontal drive signal to a second frequency related to the second resonant frequency of the horizontal deflection circuit 10, and a vertical deflection circuit 12 including means 26 responsive to the format control signal for varying the amplitude of the output of the vertical deflection circuit from a first value to a second value

• CHARACTERIZED BY:
• said horizontal deflection circuit inductance 16, 30 including a yoke 30 and said inductive value changing means 26, 40, 42, 44 including a switch 40, 42 for effectively shorting at least a portion of the turns of said yoke 30 so as to reduce the inductance of the yoke 30.