1 Title of the Invention
Increase in DVI cable length to avoid dropout of Display Identification Data
and Clock Signal
2 Field of the Invention
5 lhis invention generally relates to electronics engineering field and
particularly narrates about increase in length of DVI cable from ·host
computer to display by generating DDC lines locally.
3 · Background of the Invention
According to US 6941395, the Digital Visual Interface (DVI) is a display
1 0 interface developed in response to the proliferation of digital flat panel
display. The DVI interface is becoming more prevalent and is expected to
become widely used for digital display devices, in.duding .flat-panel display
,. .·
-and .emerging digital CATs.
A method and apparatus for transmitting a DVI signal to a remote location.
15 The method splits ·the signal into a multitude of Signals that are
transmitted down cables. The split Signals are collected into a single
signal at the receiving end at the remote location.
4 Brief Summary of the Invention
This invention provides "Increase in DVI cabl.e length to avoid dropout of
· 20 Display Identification Data and Clock Signal".
The present invention uses DDC adaptor (inside the host computer) to
provide Extended Display Identification Data (EDID) and clock signal (3.1.
V) for DOC clock.
5 Detail Description of the Drawings
· :'0::-:·~; ,~~::~.·25 ;;·: .Figure:::1: ;,~cTrcl~ir Diagram:.:.lor Host computer and Display Monitor ·(In
Normal case)
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._..._. . ._
.;~, ~~.... ".; .;, ...
Applicant: Hindustan Aeronautics Limited . ··~.1(,
Figure 2: Circuit Diagram for Host Computer and Display Monitor (with
DOC signal g_enerated through adaptor)
6 Detail Description of the Invention
This invention provides "Increase in DVI cable length to avoid dropout of
5 Display Identification Data and Clock Signal".
Display DVI signal at longer distance is always challenging due to drop out
of clock signal. Display computer (DC) .send DOC signal to display along
with extended display identification data (EDID).
Display Data · Channel (DOC) is a collection of protocols· for digital
1 0 communication between host computer and Display monitor.
The EDID stq.Jcture. includes product type, chromaticity data, timings
supported by th_e,·<;Jisplay, display size, luminance data an.d pixel mapping
data etc.
Most of thE! time EDID lost, when cable length is more than 10 meter (up .
15 to 15 meter). Most of time, user is aware about EDID details of host
computer. Same will be directly feed to HOST computer _by installing a
PCB board /adaptor inside or in close proximity of host computer to
gen-erate Clock signal (3.1- Volt for o[)c clock) inside th~ compute~ locally
by using a circuit.
20 DVI signal may be used up to 1 0 meter from host computer to extended
display, However, if distance is more than 1 0 meter, DVI amplifier is
required.
In General, (Refer Figure 1 ), Host computer (1 ), DOC lines are directly
connected to Display Monitor (2). Host computer (1) receives EDID data
25 . on ogq_limts ~IQn.g witJl.~IQc.!:s sj,gnal (3.1 volt) for clock timing of DVI data.
4.:7-... ';"':..':~~ ;:::::;: :~: ~:7'' -.... ~;~.,.;- ::·., ·.·.~~ ... ;:, ... ~- .; ....... ; .. .. ,:.:• .. ".,
In proposed invention (Refer Figure 2), Host computer (1) DOC lines are
connected through an adaptor (3) (adaptor may be installed inside the
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Applicant: Hindustan Aeronautics Limited
host computer or near the close proximity of host computer). Adaptor (3)
provides DDC clock signal of 3 .1 volts and EDID of Display monitor (3) (at
a distance of 15 Meter).
Adaptor (3) is installed near Host Computer (1 ), possibility of dropout of
5 EDID/clock signal ruled out. If DVI connections (Refer Figure 2) made·
through adaptor (3), between Host Computer (1) and Display Monitor (2),
a distance of 15 meter may be achieved.
This invention may be used to solve problems that have risen in DVI signal
where a DVI signal need to travel a long distance. The invention allows
10 use of adaptor/external adaptor for DDC and EDID signals.

We Claim,
1. The system to avoid dropout of Display Identification Data and Clock
5 Signal which is comprising of:
Adaptor (3) which generates DOC signal;
Interconnection between HOST Computer (1) and Display Monitor (2)
without adaptor {3);
Interconnection between HOST Computer (1) and Display Monitor (2)
10 with adaptor (3); and
· Transmission of extended display identification data through adaptor
.. (3) to HOST computer (1 ).