发明名称 |
Recovery of time base for teletext system - uses PLL at output of bistable circuit, with counter to reset bistable after time period |
摘要 |
<p>The time base is recovered from a composite video synchronisation signal to produce line synchronisation pulses for use in a teletext system. The output of the composite sync. circuit drives a phase locked loop to avoid disturbance to the image quality. A D-type bistable (1) receives the composite video sync. signal (V) at its clock input. The Q-output is applied to a phase locked loop (2) and to an integrator (3) which produces a sawtooth waveform which is compared with a threshold signal (5) by a comparator (7). The comparator output presets the bistable after a time period. The Q-bar output is connected to a similar integrator (10) and comparator (14) to reset the bistable after a time period. The time periods produced by the comparators provide a window for the line synchronisation signal.</p> |
申请公布号 |
FR2457615(A1) |
申请公布日期 |
1980.12.19 |
申请号 |
FR19790012909 |
申请日期 |
1979.05.21 |
申请人 |
SIGNALISATION CIE CONTINENTALE |
发明人 |
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分类号 |
H04N5/06;(IPC1-7):04N5/04 |
主分类号 |
H04N5/06 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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