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: Disclosed is a tape-transport apparatus wherein a first brake is provided for a reel for winding a magnetic tape thereon, the reel being operatively coupled to a first DC motor; a second brake is provided for a reel for supplying the magnetic tape, the reel being operatively coupled to a second DC motor; means is provided which is adapted to impart the retarding force to the second DC motor when an electromotive force, which is generated by the rotation of the first DC motor due to its inertia whenever the power supply to the first DC motor is interrupted, is in excess of a predetermined level; and there is provided means which is adapted to operate the first and second brakes when the magnitude of the electromotive force reaches a predetermined value, thereby stopping the transport of the tape.

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: In order to improve characteristics of localization of sound images and a listener's sense of stereophonic perspective, a loudspeaker system for a stereophonic sound reproduction system comprises a main speaker adapted to be driven by audio input signal and radiate acoustic energies toward a listener for stereophonic reproduction, and a subspeaker adapted to be driven by the input signal and radiate out-of-phase acoustic energies which are smaller in magnitude than the acoustic energies provided by the main speaker and reach the listener with a time delay.

Abstract: A bandwidth changing circuit comprising first and second transistors connected in differential configuration, a narrowband filter whose output is connected to an input electrode of the first transistor, and a switching circuit. The switching circuit is responsive to a wideband designation voltage signal from a control voltage source to couple a wideband input signal source to an input electrode of the second transistor, and is responsive also to a narrowband designation voltage signal to couple the wideband input signal source to the input of the narrowband filter. The second transistor is biased normally conductive, while the first transistor is biased nonconductive in response to application of the wideband designation voltage signal to the input electrode thereof and biased conductive also in response to the narrowband designation voltage, thereby constituting a differential amplifier circuit together with the second transistor.

Abstract: Disclosed is an automatic noise reduction system of FM stereo receiver wherein the input level and carrier frequency deviation of an FM stereo transmission signal received by an antenna are detected and, when at least either one of the input level and carrier frequency deviation decreases, the separation between first and second audio outputs of a stereo demodulator for demodulating the FM stereo transmission signal is decreased and simultaneously high frequency components on the first and second audio outputs are attenuated.

Abstract: This invention discloses a control circuit to be used in a decoder apparatus applicable to matrix 4-channel systems of different types. The control circuit is adapted to control, according to the type of composite signals to be decoded by the decoder apparatus, at least first and second gain control amplifiers which control the amplitude ratio between signals to be combined into output signals, and includes an FET array comprised of at least four field effect transistors formed in a semiconductor chip. First and second field effect transistors in the FET array are so connected to a DC power source that different predetermined DC currents may flow through their source-drain paths. To the first and second gain control amplifiers, third and fourth field effect transistors of the FET array are coupled respectively in such a manner that the internal resistances between their source-drain paths control the gains of the first and second amplifiers.

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: An oscillation frequency control device which comprises a voltage control local oscillator; a generator for giving forth an output having a predetermined referential frequency; means for periodically generating a gate pulse whose time width is equal to an integral multiple of the period of an output signal from said generator; a gate circuit for permitting the passage of an output signal from the local oscillator only during the time width of said gate pulse, wherein, while the local oscillator continues oscillation at a desired frequency, the number k of waves running through the gate circuit is chosen to be equal to an integral multiple of the counting capacity or the scale type n of a counter; said n-scale counter counts signals which have traveled through the gate circuit in at least one cycle for each supply period of the gate pulse, starting with the prescribed count at which said counter is initially reset; a count obtained in the final cycle is changed into an analog signal; comparison is made between

Abstract: A power amplifier is constituted by a complementary pair of one N channel and one P channel unsaturated junction type FET's constructing a single ended pushpull circuit, the N channel FET having a drain connected to the positive terminal of a first dc power source of a predetermined voltage and a source connected via a load to a ground potential, and the P channel FET having a drain connected to the negative terminal of the first dc power source and a source connected via the load to the ground potential.

Abstract: A multi-directional sound system for use in the manufacture of matrix four channel stereophono discs comprises an encoder including a plurality of phase shifters for shifting the phases of a plurality of directional input signals from discrete sound sources by angles corresponding to the directions of the sound sources and a matrix circuit for producing two channel signals, and a decoder for decoding the two channel signals for reproducing the directional input signals.