发明授权
US4419695A Television sound receiver 失效
电视声音接收器

Television sound receiver
摘要:
A television sound receiver having an input terminal for receiving a television sound signal, a tuner including a local oscillator connected to the input terminal, an intercarrier sound demodulating circuit connected to the tuner, a split-carrier sound demodulating circuit, including a limiter amplifier connected to the tuner, a sound signal output terminal, and a switching device for selectively and operatively connecting either the intercarrier or split-carrier sound demodulating circuits between the tuner and the sound signal output terminal. Additionally, the receiver includes an error detecting device connected to the split-carrier sound demodulating circuit for detecting the frequency error of the local oscillator and a first operational device which is responsive to an output signal from the error detecting device and which produces a first operational device output signal which activates the switching device such that the split-carrier sound demodulating circuit is operatively connected between the tuner and the sound output terminal when the output signal from the error detecting device is less than a predetermined level. Level detectors are connected to the limiter amplifier and detect a level of the split-carrier sound signal. A second operational device, which is responsive to the output signal from the level detectors, produces an output signal which activates the switching device such that the intercarrier sound demodulating circuit is operatively connected between the tuner and the sound output terminal when the output signals from the level detectors are less than a predetermined value.
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