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Radiated Signal Cruncher for Video Displays

IP.com Disclosure Number: IPCOM000039319D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Trong, SD: AUTHOR [+2]

Abstract

Mixing a meaningless character signal with the actual character signal to be displayed on a CRT provides a safer, and often less expensive, intelligence protection for, say, PC terminals than conventional shielding, as it simulates the presence of several active terminals, which does not allow reading the radiated signal of a specific terminal. Such a radiated signal cruncher essentially consists of two parts. A duplication of the circuitry driving the CRT and a random character generator. The random character generator takes its drive signal by random pulse selection from the actual signal to be displayed. It generates an equivalent character without significance which drives the duplicated or simulated CRT driver circuitry.

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Radiated Signal Cruncher for Video Displays

Mixing a meaningless character signal with the actual character signal to be displayed on a CRT provides a safer, and often less expensive, intelligence protection for, say, PC terminals than conventional shielding, as it simulates the presence of several active terminals, which does not allow reading the radiated signal of a specific terminal. Such a radiated signal cruncher essentially consists of two parts. A duplication of the circuitry driving the CRT and a random character generator. The random character generator takes its drive signal by random pulse selection from the actual signal to be displayed. It generates an equivalent character without significance which drives the duplicated or simulated CRT driver circuitry. The CRT radiation characteristic, as far as field strength and frequency spectrum are concerned, is simulated by an antenna or a similar structure mounted inside the display. A shift register, for example, may be used as a character generator. Other means for generating meaningless characters are known from the art. Like the actual radiated characters, the purposely generated noise does not produce susceptibility problems in the video display unit, as this noise consists of characterlike but meaningless signals.

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