| 摘要 |
An additional information f2a previously superimposed repeatedly four times with a period shorter than the decoding period of a spread information on an information signal f1a by way of spectral spread is detected four times by way of an additional information signal detection section by way of inversion spread based on a spectrally spread PN signal f5a from a PN generation section, the coincidence detection section confirms coincidence of four detection results, and thus the superimposition of the additional information f2a is finalized, therefore the additional information f2a is detected within a short time because of a short period of the spectral spread, the additional information f2a is detected with high detection accuracy with a small spread gain by way of confirming the coincidence of four detections, and a write section can perform write inhibition properly based on detection of the additional information f2a.
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