Class 381/5 - Four discrete channels

Subclass of Class 381 - Electrical audio signal processing systems and devices
Definition: Subject matter where the independent sound signals are four
No. of patents: 27
Last issue date: 03/11/2008

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Number	Title	Issue Date
7343015	Method and apparatus for high fidelity wireless stereophonic transmission utilizing dual frequency carriers A method and system is disclosed for transmitting two related channels of signals through the air. A first channel of signals is modulated with a first carrier frequency, and a second channel of signals is modulated with a second carrier frequency. The modulated fir...	03/11/2008
7149312	Method and device to retrieve RDS information To retrieve RDS information by filtering and transforming an incoming multiplex signal (m(t)) into a RDS baseband signal, an amplitude modulated RDS signal (ma(t), mc(t)) is derived on basis of an intermediate signal (ma(t)) obtained...	12/12/2006
6977653	Surround sound display A surround sound display has a graphic sound stage image, including speakers representing sources and a central listener, and bent correlation meter scales for each stereo channel. The correlation meter scales have values from +1 at one end to −1 at the other end ...	12/20/2005
6847395	Digital television signal test equipment The invention, in part, provides an integrated digital television (DTV) diagnostic instrument comprising: at least one of a video display device (VDD) and an audio display device (AudDD); DTV circuitry (AV) to receive a DTV signal, to reconstruct at least one of a v...	01/25/2005
5848129	Electronic billboard with telephone call-in control A conventional billboard for displaying a visual message is combined with a communication system for enabling a message related to the message displayed by the billboard to be transmitted from the billboard to passengers of automotive vehicles driving by ...	12/08/1998
5717765	Theater sound system with upper surround channels An improved theater surround sound system incorporates a screen top speaker and an overhead speaker driven by corresponding upper surround channels to more accurately reproduce sounds produced from above the listener. These top surround channels are encod...	02/10/1998
5471534	Devices, systems and methods for composite signal decoding employing interpolation filter A device and method for composite signal decoding is provided in which an analog-to-digital converter (15) digitizes an incoming FM composite signal. The digitized signal is filtered by an interpolator (13) which uses filter coefficients developed as a fu...	11/28/1995
4316058	Sound field transmission system surrounding a listener Systems for uniformly reproducing a sound field surrounding a listener are disclosed utilizing three channels of audio information signals. One channel provides signals representative of total sound pressure (a sum signal) and the two remaining channels p...	02/16/1982
4282401	System for transmission and reception of discrete four channel stereo A system for transmission and reception of discrete four channel stereo for utilizing a carrier frequency modulated in accordance with a modulation function of the form: where A=LF+LR+RR+RF, B=LF+LR-RR-RF, C=LF-LR=RR+RF, D=LF-LR+RR-RF, LF, LR, RR and RF are au...	08/04/1981
4245352	Automated system for testing radio receivers An automated system for electronically testing the response and the quality of the output produced by radio receivers and the like is provided, wherein various tests including frequency response, harmonic distortion, sensitivity, selectivity, signal-to-no...	01/13/1981
4131851	Radio-signal receiver with plug-in modules A receiver for radio signals, comprising an r-f (radio-frequency) unit and an a-f (audio-frequency) unit, the circuit in the a-f unit being interrupted at certain points and the receiver being devised electrically and with respect to its spatial design in...	12/26/1978
4075425	Multi-directional sound signal reproducing system The present invention is to increase the carrier level so as to improve the S/N ratio when the factor T93, TT or TQ is small in level. When the level is low, noises are apt to be offensive to a listener's ear, but the repr...	02/21/1978
4061882	Quadrature multiplying four-channel demodulator A decoder is provided for a FM radio four-channel system having the usual 19 kHz pilot signal, a first subcarrier at 38 kHz, a second subcarrier in quadrature therewith, and another subcarrier at 76 kHz. The decoder of the present invention is a time divi...	12/06/1977
4037055	Stereophonic demodulator apparatus Stereophonic demodulator system for demodulating a stereophonic composite signal that includes a subcarrier frequency of at least 38 KHz, the apparatus including: a circuit for producing a 38 KHz switching signal, a circuit for producing a 114 KHz switchi...	07/19/1977
4027107	Multiple channel FM stereo system A transmitter or a receiver processes four-channel stereo frequency-modulation information. The information represents four audio signals A, B, C and D that correspond to sources respectively located at the left-front, right-front, left-rear and right-rea...	05/31/1977
4016366	Compatible stereophonic receiver 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...	04/05/1977
4013841	Four-channel stereo receiver A four-channel stereo receiver capable of making the four-channel indication, and automatically changing over the four-channel mode operation and the two-channel mode operation or muting the monaural and the two-channel signal, based on the presence or ab...	03/22/1977
3991374	Controllable bandwidth IF filter circuit for radio receivers Controllable bandwidth IF filter circuit for radio receivers generally, but having particular application to quadraphonic radio receivers intended for use in a quadraphonic system that is compatible with existing monophonic and biphonic equipment, said fi...	11/09/1976
3985964	4-Channel stereophonic demodulating system A 4-channel stereophonic demodulating system based on a switching mode, which comprises a plurality of switching means for demodulating a received 4-channel stereophonic composite signal under control by a first and a second switching signals obtained fro...	10/12/1976
3983500	Angle modulated wave demodulation system An angle modulated wave demodulation system demodulates an input angle modulated wave by means of a phase locked loop system which comprises a phase comparator, which is operated responsive to an input angle modulated wave. A voltage controlled oscillator...	09/28/1976
3980832	Decoder for four channel FM stereophonic composite signal having an Indicating signal wherein the indicating signal is detected and used in the decoding of the four channel composite signal A decoder is provided for four channel FM stereophonic composite signals including a first pilot signal, a main channel signal, a first sub-channel signal suppressed carrier amplitude modulated on a first subcarrier having a frequency twice that of the fi...	09/14/1976
3970788	Monaural and stereo compatible multidirectional sound matrixing Multidirectional source signals which are encoded in two monaural and stereo-compatible transmission channels with predetermined amplitude and phase relations indicative of source directions and adapted to be decoded for formation of more than two loudspe...	07/20/1976
3965302	Stereo signal demodulator in a four-channel stereo broadcast receiver 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 ...	06/22/1976
3961276	Stereo signal demodulator in a four-channel stereo broadcast receiver comprising means for performing delay equalization together with sampling of a composite signal 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 sig...	06/01/1976
3944747	Multiple channel FM stereo system A transmitter or a receiver processes four-channel stereo frequency-modulation information. The information represents four audio signals A, B, C and D that correspond to sources respectively located at the left-front, right-front, left-rear and right-rea...	03/16/1976
3942126	Band-pass filter for frequency modulated signal transmission A band-pass filter comprises a delay circuit comprising a plurality of unit delay elements connected in cascade arrangement and receiving as input a signal including a frequency modulated signal and a coefficient summing circuit for carrying out coefficie...	03/02/1976
3937896	Compatible four channel radio broadcast and receiving system A compatible four channel system for use in conjunction with a radio transmission system for transmitting four individual audio signals over a medium having primary and secondary information channels and first and second subsidiary information channels, t...	02/10/1976

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Class 381/5 - Four discrete channels