| 摘要 |
In a dual-standard PAL/SECAM color TV receiver, an identification system provides a mode-switching output, permitting automatic switching of the receiver between a PAL-reception mode of operation and a SECAM-reception operating mode, in dependence upon the PAL or SECAM nature of the transmission received. In the SECAM-reception mode, a PAL decoder receives the chrominance component output of a SECAM-PAL transcoder; in the PAL-reception mode, the PAL decoder receives chrominance signals which bypass the transcoder. Luminance signal channel of the dual-standard receiver includes a switchable luminance signal delay line in cascade with a chrominance component trap circuit. Switchable delay line is controlled by mode-switching output of identification system such that delay line is interposed in luminance signal path only during SECAM-reception mode operation. Delay magnitude provided by delay line substantially matches difference in delays suffered by chrominance information during operation in the respective modes. Trap circuit, providing luminance delay substantially compensating delay suffered by chrominance information during operation in PAL-reception mode, includes resonant circuits tuned respectively to upper and lower SECAM subcarrier resting frequencies.
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