Tutorial
History Of DMX
Aug
DMX is a digital protocol for the control of stage lighting and effects. It was created to address a shortage of channels in its predecessor, LMX, also known as multiplex. LMX was similar to DMX, except it was an analog signal instead of digital, and limited to 128 channels. LMX was a 3 wire protocol using standard microphone cables with an XLR connector. DMX was an amazing development for larger shows that required more then 128 traditional fixtures on a traditional dimmer! At the time, no one imagined needing more then 512 channels.
512 Channels= A Universe
Many controllers now offer control of multiple Universes.
DMX is pretty straightforward, with 512 channels of simultaneous information, with each channel offering 256 levels of signal information. To best understand the levels each channel offers, imagine a massively long row of 512 faders. With 0 being off, and 255 would be at the very top at full brightness.
Then things got a little complicated.
Men in a Smoke Filled Back Room- Changing the Industry
The 5 Pin XLR Connector
DMX was agreed upon by some old men in a cigar filled back room as a 5 wire protocol using a shielded, twisted pair of cable that is similar to microphone cable but meeting certain resistance per foot parameters and terminated with a 5pin XLR connector.
Here’s where it gets a little confusing. Manufacturers who didn’t have representatives in that smoke filled back room said, “hey DMX is a firewire protocol where only three wires are required, why waste money on a 5 pin jack when a 3 pin jack will work.” The extra two pins have never been designated.
Since microphone cables use 3-pin XLRs exclusively, 3-pin connectors were a more affordable solution. This is not to say that microphone cables are usable as DMX cables. Read here to learn the difference.
*Who actually developed DMX was the highly respected United States Institute of Theatre Technology (or USITT). Every manufacturer who is a member of the USITT is required to provide 5-pin DMX on their fixtures. However, 3-pin has become so standard across the industry, that many provide both 3 and 5-pin connections.
DMX Basics & History Part 1 was written by our president, Peter Vaque, back in 2011 with the promise of a Part 2. When asked what ever happened to the Part 2, he replied, ” Mel Brook’s History of The World Part 1 never had a part two.” This is a valid point, and we hope you are satisfied with Part 1 of this one part series.
Thanks for Reading!
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