| 摘要 |
The Earth's magnetic field and other localised fields can cause a reduction in television picture quality by unwanted deflection of the electron beam inside the picture tube. The present system provides compensation for this effect by inducing a counter-balancing rotation of the raster. In addition to the normal dynamic beam deflection coils on the neck of the tube (41), two coils are mounted on the tube. The first coil (42) is mounted over the deflection yoke on the neck, while the second (43) is mounted around the outside of the front of the tube, just behind the screen. A d.c. current is fed to the coils (42, 43) which are connected in series. The current is supplied by a variable power supply (44), controlled by an adjustment circuit (45).
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