| Patents for H04S 3 - Systems employing more than two channels, e.g. quadraphonic (4,597) |
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| 05/05/1981 | US4266093 Compatible four channel radio broadcast and receiving system |
| 04/15/1981 | EP0027043A1 Vehicle sound reproducing apparatus |
| 04/14/1981 | US4262170 Microphone system for producing signals for surround-sound transmission and reproduction |
| 02/17/1981 | US4251688 Audio-digital processing system for demultiplexing stereophonic/quadriphonic input audio signals into 4-to-72 output audio signals |
| 02/17/1981 | US4251685 Reproduction of sound |
| 11/25/1980 | US4236039 Signal matrixing for directional reproduction of sound |
| 10/28/1980 | US4230905 Stereophonic system with discrete bass channels |
| 08/26/1980 | US4219696 Sound image localization control system |
| 08/19/1980 | US4218583 Varying loudspeaker spatial characteristics |
| 03/18/1980 | CA1073820A1 System for reducing noise transients in recorded sound signals |
| 02/06/1980 | EP0007453A1 Varying loudspeaker spatial characteristics |
| 01/29/1980 | US4186281 Multichannel record disc reproducing apparatus |
| 12/18/1979 | CA1068219A1 Surround sound reproduction systems |
| 11/27/1979 | US4176252 Multi-dimensional audio projector |
| 09/25/1979 | CA1063035A1 Sound reproduction systems |
| 09/04/1979 | CA1061721A1 Three channel sound encoding and decoding system |
| 05/15/1979 | US4155041 System for reducing noise transients |
| 05/01/1979 | US4152550 Apparatus for reproducing a multichannel record disc |
| 05/01/1979 | US4152542 Multichannel matrix logic and encoding systems |
| 04/24/1979 | US4151369 Sound reproduction systems |
| 04/10/1979 | US4149031 Multichannel matrix logic and encoding systems |
| 02/13/1979 | US4139729 Sound reproduction system with matrixing of power amplifier outputs |
| 01/02/1979 | US4132859 Sound reproducing apparatus |
| 10/17/1978 | US4121059 Sound field expanding device |
| 10/17/1978 | CA1040714A1 Transmitting and reproducing system for a plurality of audio information signals |
| 10/10/1978 | US4119798 Binaural multi-channel stereophony |
| 10/03/1978 | US4118599 Stereophonic sound reproduction system |
| 09/19/1978 | US4115666 Discrete 4-channel stereo recording and/or reproducing system compatible with matrix systems |
| 09/19/1978 | CA1038773A1 Centre channel derivation for stereophonic cinema sound |
| 09/05/1978 | US4112255 Rota-phonic system for stereo quadrophonic sound system |
| 08/15/1978 | US4107478 Angle modulated wave demodulation system |
| 08/08/1978 | US4105865 Audio distributor |
| 06/20/1978 | US4096360 Multichannel record disc reproducing system |
| 06/20/1978 | US4096353 Microphone system for producing signals for quadraphonic reproduction |
| 06/13/1978 | US4095049 Non-rotationally-symmetric surround-sound encoding system |
| 04/25/1978 | US4086433 Sound reproduction system with non-square loudspeaker lay-out |
| 04/18/1978 | US4085291 Synthetic supplementary channel matrix decoding systems |
| 03/28/1978 | US4081606 Sound reproduction systems with augmentation of image definition in a selected direction |
| 03/14/1978 | US4079330 System for demodulating angle-modulated signals |
| 02/21/1978 | US4075425 Multi-directional sound signal reproducing system |
| 02/14/1978 | US4074083 Stereophonic sound system particularly useful in a cinema auditorium |
| 02/07/1978 | US4072821 Microphone system for producing signals for quadraphonic reproduction |
| 01/24/1978 | US4070552 Multi-directional stereo multiple recording apparatus with constant acceleration cutting |
| 01/03/1978 | US4066972 System for demodulating angle-modulated signals |
| 11/29/1977 | US4060696 Binaural four-channel stereophony |
| 08/16/1977 | USRE29360 Or reproducing four channel signals on a record disc |
| 08/16/1977 | US4042779 Coincident microphone simulation covering three dimensional space and yielding various directional outputs |
| 07/19/1977 | US4037165 Synchronous signal generating system with phase-locked loop circuit |
| 05/31/1977 | US4027107 Multiple channel FM stereo system |
| 05/17/1977 | US4024344 Center channel derivation for stereophonic cinema sound |
| 05/03/1977 | US4021612 Decoder apparatus applicable to matrix 4-channel systems of different types |
| 05/03/1977 | US4021610 Control circuit for a matrixed four channel audio reproducing system |
| 04/19/1977 | US4018992 Decoder for quadraphonic playback |
| 04/05/1977 | USRE29171 Multi-directional sound system |
| 04/05/1977 | US4016374 Multichannel record disc recording system with signal level control |
| 02/01/1977 | US4006313 Transmitting and reproducing system having improved noise reduction characteristics for quadraphonic audio information signals |
| 02/01/1977 | US4006306 Audio signal processing apparatus |
| 01/18/1977 | US4004095 System for time sharing an audio amplifier |
| 01/11/1977 | US4002840 Angle-modulated signal transmission system |
| 01/04/1977 | US4001518 Discrete four-channel disc reproducing system |
| 12/14/1976 | US3997725 Multidirectional sound reproduction systems |
| 11/16/1976 | US3992590 Matrix amplifying circuit |
| 11/02/1976 | US3989903 Multi-directional sound signal recording and/or reproducing system with crosstalk compensation means |
| 10/19/1976 | US3987256 Grooved record playback system with multiple transducers |
| 10/12/1976 | US3985978 Method and apparatus for control of FM beat distortion |
| 10/12/1976 | US3985964 4-Channel stereophonic demodulating system |
| 09/28/1976 | US3983500 Angle modulated wave demodulation system |
| 09/28/1976 | US3983334 Matrix and equalizer circuit with gain control |
| 09/21/1976 | US3982071 Multichannel sound signal processing system employing voltage controlled amplifiers |
| 09/21/1976 | US3982069 Decoding apparatus for use in matrix four channel systems of a plurality of types |
| 09/07/1976 | US3979564 4-Channel stereo recording and reproducing method |
| 07/20/1976 | US3970788 Monaural and stereo compatible multidirectional sound matrixing |
| 07/13/1976 | US3969588 Audio pan generator |
| 07/06/1976 | US3968331 Encoding and decoding system for quadraphonic sound |
| 06/29/1976 | US3967063 Logic for matrix systems for reproducing quadraphonic sound |
| 06/22/1976 | US3965302 Stereo signal demodulator in a four-channel stereo broadcast receiver |
| 05/25/1976 | US3959590 Stereophonic sound system |
| 05/18/1976 | US3958085 Compatible 4-2-4 encoding-decoding system |
| 04/27/1976 | US3953686 Multichannel record disc recording system |
| 04/20/1976 | US3952157 Matrix four-channel decoding system |
| 03/30/1976 | US3947637 Signal composing circuit |
| 03/23/1976 | US3946165 Method and apparatus for control of crosstalk in multiple frequency recording |
| 03/16/1976 | US3944941 Switching circuit for use with balanced transformerless amplifier |
| 03/16/1976 | US3944755 Composite filter circuit |
| 03/16/1976 | US3944735 Directional enhancement system for quadraphonic decoders |
| 03/09/1976 | US3943303 Abnormal sound eliminating system in record disc reproducing apparatus |
| 03/09/1976 | US3943287 Apparatus and method for decoding four channel sound |
| 03/09/1976 | US3943286 Variable gain control circuit |
| 02/24/1976 | US3940698 Muting circuit |
| 02/24/1976 | US3940559 Compatible four channel recording and reproducing system |
| 02/10/1976 | US3937885 Control circuit for a matrixed four channel audio reproducing system |
| 02/03/1976 | US3936619 Four-channel stereophonic reproducing system for reproducing discrete CD-4 four-channel stereo disc |
| 02/03/1976 | US3936618 Multichannel record disc reproducing system and apparatus |
| 01/20/1976 | US3934087 Angle modulated wave demodulation system |
| 01/20/1976 | US3934086 Matrix four-channel decoding system |
| 01/13/1976 | US3932706 Signal synthesizing system adaptable for discrete four-channel sound reproducing system and matrix four-channel sound reproducing system |
| 01/06/1976 | US3931482 Four-channel stereophonic reproducing system for reproducing discrete four-channel stereophonic discs |