822 Chapter 28
The reference color burst is included on every active TV line at a point in the original
black and white signal given over to line retrace. Note also the high-frequency color
information superimposed on the “ black and white ” luminance information. Once the
demodulated signals have been through a reverse color space conversion and become
RGB signals once more, they are applied to the guns of the color tube ( Table 28.1 ).
As you watch television, three colors are being scanned simultaneously by three parallel
electron beams, emitted by three cathodes at the base of the tube and all scanned by a
common magnetic defl ection system. But how to ensure that each electron gun only
Table 28.1
NTSC PAL
Field frequency 59.94 Hz 50 Hz
Total lines 525 625
Active lines 480 575
Horizontal resolution a 440 572
Line frequency 15.75 kHz 15.625 kHz
a Horizontal resolutions are calculated for an NTSC bandwidth of
4.2 MHz and 52- μ s line period; PAL, 5.5 MHz bandwidth and
52-μ s period.Electron gunsCathode raysShadowmaskGlass screen
(phosphors
on inner face)
Figure 28.8 : The shadowmask in action.