Philips 7603 series, Руководство по обслуживанию

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Video source selection
The Composite Video Blanking Signal (CVBS) from buffer 7201 goes to the audio carrier trap filters (1200, 1201, or 1202
depending on the system used) to remove the audio signal. The signal then goes to pin 40 of IC 7200. The internal input
switch selects the following input signals:
•
Pin 40: terrestrial CVBS input
•
Pin 42: external AV1 CVBS input
•
Pin 44: external Side I/O CVBS or AV2 Luminance (Y) input
Once the signal source is selected, a chroma filter calibration is performed. The received color burst sub-carrier frequency is
used for this. Correspondingly, the chroma band pass filter for PAL/NTSC processing or the cloche filter for SECAM
processing is switched on. The selected luminance (Y) signal is supplied to the horizontal and vertical synchronization
processing circuit and to the luminance processing circuit. In the luminance-processing block, the luminance signal goes to
the chroma trap filter. This trap is switched 'on' or 'off' depending on the color burst detection of the chroma calibration
circuit.
The group delay correction part can be switched between the BG and a flat group delay characteristic. This has the
advantage that in multi-standard receivers no compromise has to be made for the choice of the SAW filter.
Figure 1