Sony Corporation

Ikuo Shimizu

Satoshi Yokoya

Masakatsu Toyoshima

Norio Numata

Michimasa Komatsubara

Keiko Ichihara

Decoding or demodulating circuitry can produce stereo right channel and left channel signals from AM stereo signals that have been coded according to any of the well known methods. A stereo sum signal made up of the left and right channel stereo signals added together, and a stereo difference signal made up of the difference between the stereo left and right channel signals are developed and fed to a matrix to interconnect these signals to extract or separate the left and right channel stereo signals. At least one of the known methods of stereo coding requires phase shifting of these two developed signals and suitable phase shift circuitry, along with a switching circuit provides the matrix with the appropriate signals when that method of stereo coding is employed at the broadcast side. The stereo sum signal is developed using envelope detection and the stereo difference signal is developed using synchronous detection, with the synchronous detector employing signals developed in the envelope detection process. When the stereo broadcasting wave belongs to the other coding systems, the stereo sum and difference signals are respectively supplied directly to the matrix circuit through the switches.

AM stereo decoder for multiple coding systems

In a teaching system having a central or master station and one or more student stations remote from the master station, there are provided, at the master station, at least one source of main signals in a first frequency band, which source may be constituted by a tape or other record player for reproducing teaching or instructional materials, a microphone or other source of audio signals from a proctor or supervisor of the teaching system, and a source of control signals which may include address signals for identifying one of the student stations and command signals for controlling various operations of the addressed student station. The audio and control signals are employed to modulate respective carriers so as to provide first and second auxiliary signals, respectively, in frequency bands which are removed from each other and from the first frequency band of the main signals, whereupon the main signals and the first and second auxiliary signals are multiplexed to provide a composite signal which, in turn, modulates a carrier of predetermined frequency suitable for being transmitted to each of the student stations.

Signal transmission in teaching system

A radio receiver with a phase-locked loop demodulator is described. The phase-locked loop includes a phase comparator, a variable frequency (voltage-controlled) oscillator, and a low pass filter. The capture range and lock range of the phase-locked loop are controlled in response to the tuning of the loop. In an AM receiver with a phase-locked loop the variable frequency oscillator of the loop supplies a reference carrier for a synchronous detector which is phase-locked to a modulated carrier. A band pass filter eliminates undesired modulation of the variable frequency oscillator by an undesired received signal.

Radio receiver with a phase locked loop for a demodulator

A receiver having a circuit producing a control signal that has an amplitude proportional to the intensity of an input signal, and a control circuit permitting the passage of high frequency components of a low frequency signal therethrough or preventing the passage thereof, as determined by the control signal. The receiver further includes a control circuit that permits passage of low frequency components of the low frequency signal or prevents passage thereof, as determined by the control signal.

Growing community of inventors

Tokyo, Japan

Ikuo Shimizu