| 摘要 |
1,180,577. Colour television. RCA CORPORATION. 20 Feb., 1968 [24 Feb., 1967], No. 8835/67. Heading H4F. Relates to apparatus for providing selective identification and display of the four unique fields in a PAL colour television system to allow examination of the PAL waveform in the vicinity of the field sync interval. In a first embodiment where the PAL signal waveform to be monitored also includes a half-line frequency master binary output (related to the line-by-line switching of the sync burst phase), trigger pulse generation is achieved from the relationships between the sync pulse and master binary waveforms peculiar to particular fields. Switch selection of particular combinations of sync pulse responsive signals and master binary wave responsive signals enables selective generation of trigger pulses for initiating the display of any particular one of the fields of the four field sequence. In a second embodiment the distinctive make-up of the PAL composite video signal waveform alone (in particular the timing of the first colour burst with respect to the vertical sync pulses for each field) is utilized to identify the particular fields in the four-field sequence. Further, utilizing the second embodiment the field phase coincidence of differently sourced PAL signals may be determined. The four unique vertical blanking interval waveforms may be simultaneously displayed one above the other in a predetermined position sequence. |
