Elation Professional Compu Live Laptop PC - Manual (Page 104)

Compu Live VI Appendix
VI Appendix
1. DMX512 brief description
By the time you are done reading this section, you will understand how DMX works and why the
lighting world uses this standard communication protocol. For a more technical and detailed description,
please visit www.dmx512-online.com
1. The need for a standard
About 20 years ago, most lighting and console manufacturers had their own proprietary communication
protocols. During installations, it was necessary to use all lighting fixtures from the same manufacturer,
of course with their own controller board. If you wanted to use lighting fixtures from different
manufacturers (even simple dimmers), each group required their own lighting desk. It is clear that a
standard form of communication between controllers and the fixtures was necessary.
2. Understanding DMX
To understand the DMX512 communication protocol (commonly referred to as “DMX”), we will
use the “Cable TV” analogy.
Imagine a simplistic cable TV system, with only 4 relevant parts:
a. TV station
b. cable
c. decoder
d. TV set
The TV station broadcasts a signal that travels through a cable network until it reaches a decoder. The
decoder receives information on hundreds of channels, but only displays on the TV set the information
(in this case video and audio) from that single channel that we select. The TV set ignores the
information from any channel that is not selected. It only displays the information from the channel
selected in the decoder.
DMX can be related to this cable TV system, where:
a. the TV station is the controller (Compu Live)
b. the cable is a DMX cable
c. the cable decoder is the DMX decoder (which usually is inside each lighting fixture)
d. the TV set is the lighting fixture
In DMX, the number of channels that are broadcasted is always 512. Maybe some of them will be
empty or unused, but they are still broadcasted because it is a necessary component of the standard.
So, the controller sends out a signal (512 channels of information), which travels through a DMX cable
until it reaches the decoder inside the lighting fixture. In the same way you set the channel you want to
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