| 摘要 |
THERE IS PROVIDED A CIRCUIT AND METHOD FOR GENERATING A FOCUS VOLTAGE HAVING A PREDETERMINED WAVEFORM AND MAGNITUDE FOR APPLICATION TO AN ELECTRON BEAM FOCUS MEANS OF A CATHODE RAY TUBE HAVING A DISPLAY SURFACE. A HORIZONTAL DEFLECTION CURRENT (IP1) HAVING A PREDETERMINED WAVEFORM AND A FREQUENCY WHICH IS SELECTABLE OVER A PREDETERMINED RANGE OF FREQUENCIES IS USED TO GENERATE SUBSTANTIALLY HORIZONTAL SCAN LINES (221, 222, 223) ON THE DISPLAY SURFACE OF THE CATHODE RAY TUBE BY CAUSING AT LEAST ONE ELECTRON BEAM TO SWEEP ACROSS THE DISPLAY SURFACE. THE CIRCUIT (100) HAS AN INPUT (171) FOR RECEIVING A SIGNAL (IP2) HAVING A CURRENT WAVEFORM REPRESENTATIVE OF THE WAVEFORM AND FREQUENCY OF THE HORIZONTAL DEFLECTION CURRENT. IN RESPONSE TO THE RECEIVED SIGNAL, THE CIRCUIT PRODUCES A FOCUS VOLTAGE OUTPUT, THE WAVEFORM AND MAGNITUDE OF WHICH REMAIN SUBSTANTIALLY CONSTANT OVER THE RANGE OF SELECTED FREQUENCIES OF THE HORIZONTAL DEFLECTION CURRENT (IP1).
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