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EP0104724A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Visual display unit with colour control circuit

Assignee: Unisys Corp
•
Filing: 1983-07-29
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Granted: —
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Expires: 2003-07-29
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Abstract

Abstract A video display unit controls the background and cursor colours so as to ensure that the cursor is always clearly visible. <??>The foreground colour signals and the background and cursor colour signals are supplied alternately to the cathode ray tube (10) through a multiplexer (26). The background colour signals are supplied to this multiplexer through a set of EXCLUSIVE OR gates (55, 56, 57) from a strobed background colour source 38, and the other inputs of these OR gates receive the cursor time signal, thereby ensuring that the background and cursor are displayed in complementary colours. A pulse width control circuit (47-52) enables the width of the strobe pulses for the background colour signal to be varied so as to allow the brightness of the background to be adjusted.

Inventors

  • 👤 Wayne Demont Bell
  • 👤 Thomas Karl Mcfarland

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-09 13:15
CPC Classifications
G; G09; G09G; G09G5/00; G09G5/02; G09G5/024

Claims Analysis

Total Claims: 4
Claim 1
Independent Claim 84 words
A video display unit comprising a colour cathode ray tube and colour control circuits including a source of strobed background colour signals (38, 47-52) gating means (41) receiving the strobed colour signals and a cursor time signal as its inputs and providing colour output signals to a multiplexer (26), which in turn supplies alternately foreground colour signals and background or cursor colour signals to the cathode ray tube, the gating means (41) ensuring that the cursor colour signals differ from the background colour signals.
Claim 2
Dependent Claim 84 words
A video display unit comprising a colour cathode ray tube and colour control circuits including a source of strobed background colour signals (38, 47-52) gating means (41) receiving the strobed colour signals and a cursor time signal as its inputs and providing colour output signals to a multiplexer (26), which in turn supplies alternately foreground colour signals and background or cursor colour signals to the cathode ray tube, the gating means (41) ensuring that the cursor colour signals differ from the background colour signals.
Claim 3
Dependent Claim 60 words
A video display unit according to claim 1 in which the gating means (41) comprises a set of EXCLUSIVE OR gates (55, 56, 57), one for each colour component, and each receiving a colour component signal as one input and the cursor time signal as the other input, thereby ensuring that the background and cursor are displayed in complementary colours.
Claim 4
Dependent Claim 37 words
A video display unit according to claim 1 or claim 2 in which the strobed background colour signal source includes means (53) for adjusting the strobe pulse width, thereby enabling the background colour brightness to be adjusted.

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