| 摘要 |
In a television receiver with multi-standard sound, circuit means are provided which automatically detect the sound standard received in each case from the received signal. From this, a manipulated variable is derived which automatically initiates the switch-over operations necessary with the individual standards. In this connection, it is known to convert the received sound carrier, using a variable-frequency mixing carrier, to a sound carrier having a frequency which is identical with all standards and which is then supplied to an FM demodulator via a filter. It is the object to create a detection circuit which responds reliably and unambiguously and which, in particular, can be integrated well. To detect the standard, the frequency (fLO) of the mixing carrier (LO) is changed in steps. The output of the filter (40) is connected to an amplitude detector (42), the output of which is connected via an A/D converter (31) to a processor which generates a manipulated variable identifying the respective standard from the correlation between the occurrence of a carrier at the output of the filter (40) and the frequency (fLO) of the mixing carrier (LO). Especially for a multi-standard television receiver for optionally receiving sound carriers according to the M, BG stereo, I, DK standards. <IMAGE> |
