Apparatus and method for inspecting magnetic tape recorded material for alterations
US4404603A · kind A · utility
Inventors
Key dates
| Filing date | May 27, 1980 |
| Grant date | Sep 13, 1983 |
| Priority date | — |
| Expiry date | May 27, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B27/36
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for automatic high speed inspection of information recorded on magnetic video tape to determine if the original recording has been altered by erasure or over-recording has been added to in a previously unrecorded portion of the tape. To facilitate the inspection, a low frequency signal is added to the audio track of the tape at the time the original recording is made. Inspection consists of sensing the tape's video control track and the audio track containing the added low frequency signal while rewinding the tape at high speed. During rewind, sensing means positioned on the backside or non-oxide coated surface of the tape receives signals from both the video control track and audio track. The detected signals are processed by an error detection circuit where they are analyzed to determine the tape speed, control track pulse amplitude, audio signal amplitude, control track pulse pattern, and low frequency audio signal pattern. A tape without alterations is indicated by the simultaneous presence of both the added low frequency audio track signal and video control track signal. Appearance of either signal alone indicates an alteration in the tape and its locati…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.