| 摘要 |
A multi (e.g. PAL or NTSC) standards chrominance processing circuit contains a common front-end circuit portion 4, leading to circuit portions which are automatically sequentially switched (16, 17, 27, 35) from one standards operating mode to another until circuitry (45) (e.g. detecting the level of the colour burst signal, passed by a band pass filter 2, having its centre frequency switched from PAL to NTSC sub carrier and back) determines that the switched mode equates to the received television signal, whereupon a holding means 46 prevents further switching. <IMAGE> |
