Decoder for a recorder-decoder system
US4706282A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 23, 1985 |
| Grant date | Nov 10, 1987 |
| Priority date | — |
| Expiry date | Dec 23, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2020/10546
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An improved decoder for a recorder-decoder system wherein a threshold level detector is included in the decoder. The recorder provides for the recording of an audio signal plus a data signal. The data signal includes zero crossing information for sequential increments of time plus an indication of whether the threshold level was met for an increment of the recorded audio. Upon playback the decoder also provides a data signal based on the recorded audio. The threshold level detector of the decoder is higher than that of the recorder. If the recorded data signal indicates the threshold was not met and the same threshold indication is not provided by the threshold level detector of the decorder for the corresponding increment of the recorded audio signal, tampering of such audio increment of the recorded audio is considered to have occurred.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.