Abstract: A videodisc playback system is equipped with a reading device that sequentially reads the key code signals recorded on a videodisc in order to discriminate field, frame, or track. A mistracking pulse generator temporarily stores two key code signals that were consecutively read from the reading device, compares the two stored key code signals and detects the occurrence of mistracking from the two key code signals, and at the same time, generates mistracking pulses in an expanded blanking time, in a number that corresponds to the number of tracks travelled in the opposite direction to the playback shifting direction when the mistracking was detected. A forced driving device forcibly shifts the playback tracks one track at a time in the playback shifting direction with every mistracking pulse impressed from the mistracking pulse generator.

Abstract: A videodisc playback system is disclosed which enables repeated reproduction of signals recorded on a videodisc. The system comprises the usual means to mount and rotate the videodisc to be played back and a shifting device that shifts the scanning position of a read-out device in a radial direction of the videodisc. A tracking control device controls the shifting device so that the scanning position of the read-out device is on the track. Further, the system includes fast playback circuitry which causes fast playback of the videodisc by shifting playback tracks N multiple number of times, one track at a time to the next adjacent track, during one revolution of the videodisc. Repeated reproduction of signals is accomplished by circuitry connected to the fast playback circuitry that causes a predetermined number of tracks to be repeatedly played back, the predetermined number being an integral number of N.

Abstract: As many as four kinds of high-speed playback of a videodisc can be selected with only two operating switches. This is accomplished by extracting the vertical synchronizing signal from the composite video signal read from the videodisc and, based on this vertical synchronizing signal, producing more than one pulse delayed by a prescribed time. The vertical synchronizing signal and/or the delayed pulses are gated by independently outputted forward or reverse indicator signals for high-speed playback. High-speed playback is executed by forcibly driving the target tracking unit one track at a time in the direction designated by the indicator signal more than twice during the substantial vertical blanking time of the television image corresponding to the gated vertical synchronizing signal and/or the delayed pulses. When the forward and reverse indicator signals are both generated, an even higher speed playback is obtained.

Abstract: A circuit for reproducing a clock signal from digital signals reproduced from a recording medium makes self-clocking possible. The circuit includes a phase lock loop having a voltage-controlled oscillator that generates an oscillation output at a frequency which is approximately equal to or an integral multiple of the frequency of the clock signal contained in the reproduced signal. A pulse generating device outputs pulses of a fixed amplitude, triggered by the leading or trailing edge of the input signal, to the phase lock loop. An oscillation device outputs pulses having approximately the same period as the clock signal period. The oscillation device is triggered by the leading or trailing edge of the input signal. A selecting device gates the output pulses of the oscillation device to the phase lock loop.

Abstract: A circuit device for generating a synchronous signal in synchronism with a steady wave component of an input signal and including a first phase-locked loop using the input signal as a reference signal, a second phase-locked loop using an output signal of a voltage controlled oscillator (VCO) of the first phase-locked loop as a reference signal, and a feedback circuit for feeding back and adding an output signal of a VCO of the second phase-locked loop to the input signal. The synchronous signal is stably obtained at the output of the VCO of the second phase-locked loop, even if the level of the steady wave component is relatively low. The level of the fed back signal may be controlled in response to the level of the steady wave component whereby the oscillation of the circuit device may be prevented.

Abstract: An AM sterophonic broadcast signal for transmitting stereophonically related first and second audio information signals to at least one receiver comprises a first carrier component, a double-sideband component of a second carrier component being suppressed-carrier amplitude-modulated by the first audio information signal and a double-sideband component of a third carrier component being suppressed-carrier amplitude-modulated by the second audio information signal phase-shifted by 90 degree relative to the first audio information signal. The second and third carrier components have the same frequency as the first carrier component and their phases are advanced and retarded in phase by 45.degree. with respect to the first carrier component respectively. The AM stereophonic broadcast is compatible with an existing AM monophonic receiver. An AM stereophonic receiver compatible with an existing AM monophonic broadcast is also disclosed.

Abstract: An AM stereophonic transmission system in which a carrier wave signal is phase- or frequency-modulated by an audio composite signal L - jR or L + jR and the phase- or frequency-modulated carrier wave signal is further amplitude-modulated by an audio composite signal L + jR or L - jR.

Abstract: A compatible stereophonic receiver capable of receiving a monaural signal, 2-channel stereophonic composite signal and multi-channel composite signal transmitted in the frequency modulated form, which comprises a plurality of band amplifiers each having a bandwidth different from each other so as to amplify an intermediate frequency signal including any of the above-mentioned signals; a discriminator for determining whether the signal received is a monaural signal, 2-channel composite signal, or multi-channel composite signal; and means for selectively connecting a band amplifier which has a bandwidth corresponding to an output signal from the discriminator to a multiplex demodulator through a frequency modulated wave detector and controlling the multiplex demodulator to demodulate an audio signal from the output of the frequency modulated wave detector.

Abstract: Improvements in a stereo signal demodulator of a receiver in a four-channel stereo system, in which system upon transmitting four sound source signals (LF, LB, RF and RB) from one station, the transmission is carried out for a synthesized signal composed of a signal in a main channel of (LF + LB) + (RF + RB), a pilot signal, a signal in a first sub-channel consisting of a double side-band signal obtained by modulating an m-multiple frequency-multiplied signal of the pilot signal with a signal of (LF + LB) - (RF + RB), a signal in a second sub-channel consisting of a double side-band signal obtained by modulating the same, m-multiple frequency-multiplied but phase-shifted signal with a signal of (LF - LB) + (RF - RB), and a signal in a third sub-channel consisting of a single side-band signal (SSB or VSB) obtained by modulating an n-multiple (m < n) frequency-multiplied signal of the pilot signal with a signal of (LF - LB) - (RF - RB).

Abstract: A composite signal for a four-channel stereo broadcast includes a main channel component, first and second sub-channel components and at least one pilot signal. The composite signal is fed to a stereo signal demodulator through an FM tuner. The stereo signal demodulator derives the pilot signal out of the composite signal to produce first and second sampling pulse series, each sampling pulse having a different repetition frequency. The first sampling pulse series is fed to a delay circuit that is provided with electronic delay lines such as dynamic shift registers. The delay circuit is switched by the first sampling pulse series for sampling the composite signal, to shift sampled values. Sampled values delayed in the delay circuit are fed to a logical circuit to derive the main and first sub-channel components. The second sampling pulse series is supplied to a switching circuit for demodulating the second sub-channel component.