| 摘要 |
Bistandard television receiver for signals modulated in frequency, either in PAL or NTSC, or in MAC, with a demodulator arrangement having upstream of a frequency demodulator (5) a varialbe tuning frequency filter (4) controlled at the frequency of the input signal by a feedback returning, in PAL or NTSC, the demodulated signal from the demodulator to the tuning control input of the filter via a first loop having a low-pass filter (7), and a second loop having a bandpass filter (9). The demodulator arrangement includes an adder (8) for adding the signals from each one of the two loops and for applying them to the tuning control input (13) of the filter. The low-pass filter of the first loop is the only phase-shifting element of this loop and, for adapting the television receiver to the MAC standard, the arrangement is simply provided with a switch (12) for rendering the second loop inoperative.
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