EP0235947A2
Expired / Lapsed
EP
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Video display unit
Assignee: Fujitsu Services Ltd
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Filing: 1987-02-02
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Granted: —
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Expires: 2007-02-02
Abstract
Abstract A video display unit is described in which the display is divided into segments, and the order of scanning within each segment is scrambled. A segment may consist, for example, of a row or characters. The scrambling eliminates or reduces the risk of eavesdropping on electromagnetic radiation from the video signal.
Inventors
- 👤 Ian Douglas Macarthur
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 12:27
CPC Classifications
G; G09; G09G; G09G1/00; G09G1/06; G09G1/14; G09G1/16; G09G1/04
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
47 words
A video display unit having a raster-scanned display 10 arranged to receive a video signal, characterised in that the display 10 is divided into a plurality of segments each consisting of a plurality of adjacent scan lines, and the order of scanning within each segment is scrambled.
Claim 2
Dependent Claim
47 words
A video display unit having a raster-scanned display 10 arranged to receive a video signal, characterised in that the display 10 is divided into a plurality of segments each consisting of a plurality of adjacent scan lines, and the order of scanning within each segment is scrambled.
Claim 3
Dependent Claim
50 words
A video display unit according to claim 1, comprising means 22 for scrambling the order in which the scan lines within each segment appear in the video signal, and means 20 for producing an additional deflection to ensure that each scan line appears in the correct position in the display.
Claim 4
Dependent Claim
75 words
A video display unit according to claim 2, comprising means 15 for producing a scan line address indicating the scan line within the segment currently being scanned, means 22 for producing a scrambled scan line address, and subtractor means 23 for subtracting the scrambled scan line address from the scan line address to produce a signal representing the difference in position between the line currently being scanned and the line represented in the video signal.
Claim 5
Dependent Claim
31 words
A video display unit according to claim 3, wherein the means 22 for producing the scrambled scan line address comprises a shuffle circuit 30 arranged to scramble the scan line address.
Claim 6
Dependent Claim
32 words
A video display unit according to claim 3, wherein the means for producing the scrambled scan line address comprises a generator 50, 51, 52 arranged to generate sequences of scan line addresses.
Claim 7
Dependent Claim
24 words
A video display unit according to claims 2 to 5, wherein the means for producing said additional deflection comprises an additional vertical deflection coil.
Claim 8
Dependent Claim
26 words
A video display unit according to claim 6 comprising means for compensating for variations in the sensitivity of deflection produced by said additional deflection coil 20.
Claim 9
Dependent Claim
16 words
A video display unit according to any preceding claim wherein said segments comprise rows of characters.
Claim 10
Dependent Claim
18 words
A video display unit according to any preceding claim, wherein the scrambling is varied in each successive segment.
References Cited (Backward Citations)
No citation records indexed.
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