| 摘要 |
<p>A teletext decoder includes a data acquisition and control circuit (DAC) which may be operated in either of two modes under the control of a microcontroller (MC). In one mode a framing code window used for detecting a framing code in received data pulses (D) is generated internally and is used in conjunction with data lines of a received video signal where teletext data is expected to occur. In the other mode a framing code window is generated externally by means of an applied line sync signal (S) and is used in conjunction with lines of a received video signal where teletext data is not expected to occur e.g. during ITS lines and normal picture lines. In this way the problem of "junk" data is greatly alleviated.</p> |
