| 摘要 |
The invention is related to a cathode ray tube of the index type ( 1 ). Tracking elements ( 16,18 ) from a tracking structure flank, preferably above and below each phosphor element ( 20 ), being provided on an inner surface of a screen ( 10 ). A tracking signal that is derived from response signals from the tracking elements, is used to keep the electron beam ( 7,8,9 ) on the right phosphor element. In the index tube according to the invention a part of the tracking lines is provided with gaps ( 30, 30 '). The gaps generate an interruption in the tracking signal. This interruption can inter alia be used to derive the precise position of the electron beam ( 7,8,9 ) on the screen ( 10 ), especially during the star-up phase of the tube.
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