| 摘要 |
In television receivers with two-channel sound section, during transmissions with monaural accompanying sound in which the second sound carrier of 5.74 MHz is not radiated, to avoid the noise of the circuit for evaluating the identification signals on the 54.68 kHz pilot carrier, which is not driven in this case, from causing the operating mode switching to jump from monaural to binaural or stereo reproduction and thus noise interference from being transmitted to the loudspeaker in the idle right-hand channel, it is proposed to select from this noise voltage a frequency component of > 54 kHz, to rectify this noise spectrum and to use the direct-voltage potential thus formed to force the operating mode switch for the sound section into the "mono" operating mode.
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