| H | SK | ELECTRICITY |
| H04 | KL | ELECTRIC COMMUNICATION TECHNIQUE |
| H04S | UKL | STEREOPHONIC SYSTEMS [3] |
| H04S 1/00 | HGR | Two-channel systems (H04S 5/00, H04S 7/00 take precedence) [3, 2006.01] |
| H04S 3/00 | HGR | Systems employing more than two channels, e.g. quadraphonic (H04S 5/00, H04S 7/00 take precedence) [3, 2006.01] |
| H04S 3/02 | UGR1 | | . | of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other [3, 2006.01] |
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| H04S 5/00 | HGR | Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation [3, 2006.01] |
| H04S 5/02 | UGR1 | | . | of the pseudo four-channel type, e.g. in which rear channel signals are derived from two-channel stereo signals [3, 2006.01] |
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| H04S 7/00 | HGR | Indicating arrangements; Control arrangements, e.g. balance control [3, 2006.01] |