Abstract: A power source for an electronically tuned tuner in which a horizontal deflection circuit supplies high voltage power to a fly-back transformer, supplying power to the tuner, when a television signal is received but otherwise a battery source is switched into supplying the tuner. The change-over circuit may be realized by a relay, by transistors or by diodes.

Abstract: A multivoice demodulator circuit in which a sub-signal is separated from the main signal. The sub-signal may have different content and characteristic dependent upon the reception mode of the original signal. The sub-signal is given different frequency characteristics dependent upon the reception mode.

Abstract: A signal receiving system for a TV receiver incorporates at least two independent front end circuits for frequency-converting antenna signals to a lower frequency, with the output signals from these front end circuits being utilized separately to derive the video and audio signal components of the TV signal. Independent control of AGC applied to the audio and video signal components respectively can thereby be implemented, or, in the case of diversity reception using two or more antennas, the optimum antenna for reception of the video and audio signal components respectively can be selected in a mutually independent manner, to thereby attain substantially improved diversity reception, e.g. for a TV installation in a moving vehicle.

Abstract: In a sound multiplex television tuner, when the input field strength becomes smaller than a certain value, a level control means continuously attenuates the sub signal demodulation output with the aid of the field strength detection signal which a field strength detector circuit provides according to the input field strength. The characteristic of response to input field strength of the level control means is switched, according to a given sound multiplex mode, so that its operation becomes most suitable for the sound multiplex mode, thereby to suppress the noise without causing the television viewer to feel a sense of incongruity in the perceived sound.

Abstract: A multiplex sound receiver in which a detection signal is extracted from a broadcast to indicate whether the broadcast is monaural, stereo, or multi-lingual. The detection signal is used for controlling the separating of the channels. According to the invention, the detection signal is processed in accordance with the strength of the broadcast or the noise level. For instance, the detection signal is integrated over a period that is increased when the field strength decreases.

Abstract: A noise eliminating circuit including a subsignal modulator circuit, a matrix circuit, and sample-and-hold circuits, for reducing signal distortion as well as preventing the in-circuit generation of noise. The sample-and-hold circuits are disposed in the signal paths of a main signal and the demodulated subsignal and are operated by a signal synchronous with a noise component. The holding times of the two sample-and-hold circuits may be made different from one another.

Abstract: An FM receiver including a noise suppressing circuit in which the signal from which the noise is detected is taken from a front-end section of the receiver and a correction to the noise is made prior to the detector of the receiver. The noise is suppressed by terminating the received signal upon detection of the presence of noise and holding the level which was present before the noise was detected for a predetermined period of time. By detecting the noise in a signal from the front end of the receiver and by making the correction prior to the detector circuit, only a very short predetermined time period need be used and no complicated pilot signal processing circuit is required.

Abstract: An FM receiver including a noise pulse detection circuit which receives an FM detected signal containing a pilot signal and produces a control signal when a noise pulse is detected. A gate is operable to interrupt the transmission of the FM detected signal to the subsequent stage for the duration of the presence of the noise pulse responsive to the control signal and a holding circuit holds the FM detected signal of the level immediately before the interrupting operation of the gate. A multiplex demodulator receives outputs of the gate and the holding circuit for demodulating an applied FM detected signal. A signal generator is provided in the multiplex demodulator for generating a signal whose frequency and phase are same as those of the pilot signal. A superimposing circuit superimposes a signal obtained from the signal generator on the output of the holding circuit for the duration of the presence of the noise pulse.

Abstract: An FM stereophonic receiver includes a muting circuit for interrupting or reducing its signal reproduction output according to the electric field strength and a mode changing circuit for changing its reproduction mode to a stereophonic reproduction mode or a monaural reproduction mode according to the electric field strength. In the receiver, manual switches are operated to switch the muting operation point of the muting circuit and the stereophonic and monaural change-over point of the mode changing circuit, whereby the signal reproduction conditions can be suitably selected according to the choice or wish of a user.

Abstract: A muting control circuit for an FM receiver provides rapid on-off response during channel selection or tuning, and rapid on but delayed off response during listening, whereby annoying muting circuit switching is reduced. The delay is implemented by rapidly charging a capacitor when the muting is switched on, and then allowing the relatively slower discharge of the capacitor to prolong the muting operation after the control signal therefore is terminated.

Abstract: A noise limiting circuit for an FM stereo receiver comprises a filter circuit 13 for grounding high frequency components in the detector output signal through a transistor switch 14 in response to a low field strength signal supplied by the IF amplifier. The filter circuit, when activated, also grounds the 19 KHz pilot signal to automatically switch from a stereo to monaural mode, which further improves the S/N ratio. The pilot signal grounding effect may be enhanced by including an inductor in the filter circuit which, in combination with the filter capacitor, is tuned to the pilot signal frequency. The transistor 14 is switched in a rapid on -- slow off mode by providing a storage capacitor 20 and discharge resistors 17, 19 in the base control circuit of the transistor, and the filter switching or squelch level may be adjusted by a variable resistor 22.