Mitch Hefter
ESTA /USITT DMX512 Revision (ANSI E1.11) Task Group Chair

The American National Standards Institute (ANSI) approved the new version of DMX512 on November 8, 2004. This revision to USITT DMX512/1990 is formally known as "E1.11-2004 — Entertainment Technology - USITT DMX512-A — Asynchronous Serial Digital Data Transmission Standard for Controlling Lighting Equipment and Accessories." E1.11 (aka USITT DMX512-A) was developed under the ESTA Technical Standards Program by the Control Protocols Working Group with input from the entertainment industry. Publication is expected before the end of 2004.

What brought us to this point?
Before DMX512, most manufacturers had their own dimmer control protocols that were proprietary and incompatible with other manufacturers' equipment. As the industry grew and shows became more complex, the need for cross-manufacturer compatibility became critical. In 1986, the USITT Engineering Commission sponsored a session at the Annual Conference in Oakland, California. From that session, a project started that resulted in USITT DMX512 - Digital Data Transmission Standard for Dimmers and Controllers. Minor revisions were made in 1990. The physical part of the DMX512 standard is based on EIA-485, and the protocol part is based on Colortran's D192 (CMX) protocol. The expectation was that proprietary protocols would normally be used, but when there was a need to mix manufacturers in a system, users would switch over to DMX512. DMX512 was intended to be a lowest common denominator protocol. Little did we know it would become the primary protocol and help transform the industry.

The Need to Revise
Unfortunately, in 1998 it became evident that additional updates to the standard were necessary and that formal recognition through an internationally recognized standards organization was required. In March of 1998, USITT transferred maintenance of DMX512 to the ANSI Accredited Technical Standards Program of ESTA.

The revision effort was taken up by the ESTA Technical Standards Program's Control Protocols Working Group, which appointed a task group to develop the revised standard. Over the next six years, including three formal public reviews, USITT and ESTA solicited input on drafts of a revised and updated version of DMX512.

Proposals that compromised backward compatibility unfortunately had to be rejected. In total, there were eight full draft revisions prepared, each with several "sub-versions." Over 955 comments were received during the six years, and each one was addressed and resolved by the Task Group. USITT DMX512/1990 is five pages long plus a cover. ANSI E1.11-2004 will be closer to 60 pages.

What's In It for the End User?
This process introduced some new concepts, (For more details, see the USITT DMX512 web page.) The result is a more precise standard resulting in more reliable and compatible systems with recognition by formal standards-making bodies. Most importantly, end users will:

• not normally need to change their existing practices
• not normally need to modify compliant "legacy" equipment
• be better able to troubleshoot and resolve problems when they do occur

Karl Ruling, ESTA's Technical Standards Manager, states, "E1.11 is a significant improvement over its predecessor, USITT DMX512/1990, in that it clears up some of the technical ambiguities in that original, very short document, and it opens up some extensions that will allow for new protocols such as E1.20 (RDM). E1.11 has been written, however, with the intention of not making products that fully comply with USITT DMX512/1990 instantly obsolete."

USITT Fellow Mitch Hefter has a long history with DMX512 - he was Engineering Commissioner when the Oakland Conference session started DMX512. Mitch has been working in lighting controls for over 26 years. In addition to his multiple roles with USITT and ESTA, during the day he is the Senior Project Engineer for USITT Contributing member Entertainment Technology (division of the Genlyte Group) where he works in system design and project management.

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