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A DMX 512 HANDBOOK

DMX 101: A DMX 512 Handbook

Handbook Revision:

May 2008

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Table of Contents

1. Introduction to DMX ...................................................................................................................................... 4

2. Industry Standards ..........................................................................................................................................5

2.1 USITT ..................................................................................................................................................... 5

2.2 ESTA ...................................................................................................................................................... 5

2.3 ANSI ....................................................................................................................................................... 6

2.4 EIA/TIA .................................................................................................................................................. 6

2.5 References............................................................................................................................................... 6

3. Theory of Operation........................................................................................................................................ 7

3.1 The Cable TV Analogy........................................................................................................................... 8

3.2 DMX Communications......................................................................................................................... 11

3.3 Summary............................................................................................................................................... 13

4. Protocol Specifications ................................................................................................................................. 14

4.1 Connectors ............................................................................................................................................ 15

4.2 Cabling.................................................................................................................................................. 16

4.3 Data....................................................................................................................................................... 17

5. Sample Applications ..................................................................................................................................... 18

5.1 Dimmer Control.................................................................................................................................... 19

5.2 Intelligent Fixture Control .................................................................................................................... 20

5.3 Dimmer & Intelligent Fixture Control.................................................................................................. 21

5.4 Distributed Control ............................................................................................................................... 22

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DMX 101: A DMX 512 Handbook

1. Introduction to DMX

This handbook is designed to promote basic understanding of the DMX 512 protocol, including theory of
operation, proper equipment use, and some basic application examples.

DMX is an acronym for Digital Multiplex, a communication protocol (a set of rules) used to remotely control
lighting dimmers and intelligent fixtures. It is designed to provide a common communications standard between
these lighting devices regardless of the manufacturer.

The 512 after the DMX refers to the number of control channels used on one network segment (often called a
‘universe’) of devices. In a simple dimming system, one channel controls the intensity of one dimmer. A single
intelligent fixture, however, may require several channels to control its various parameters (one channel each for
pan, tilt, color, gobo, etc.).

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A basic dimming control console (such as the 16 channel Elation Stage-Setter 8) may support only a few of the
512 available channels. Many professional control consoles (such as the 3 universe, 1536 channel Elation Show
Designer 3) support multiple universes, allowing for thousands of control channels.

The topics this handbook will cover are:

• Industry Standards

• Theory of Operation

• Protocol Specifications

• Sample Applications

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2. Industry Standards

About 20 years ago, most manufacturers used their own, proprietary control protocols. This forced system
designers to use only fixtures and control consoles from the same manufacturer. There was no control standard
to allow the use of different products.

A standard is a set of widely agreed-upon guidelines for interoperability at both communications and mechanical
levels. Standardization of protocol and equipment provides many benefits to manufacturers and end users.
These benefits include:

• Increased product quality and safety

• Reduced development time and cost

• Sound engineering practices

• Protection against obsolescence

The following organizations have developed standards that relate directly to the DMX 512 protocol:

• USITT

• ESTA

• ANSI

• EIA/TIA

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2.1 USITT

The United States Institute of Theatre Technology (USITT) supports, develops, and promotes a wide variety of
standards for the theatrical and entertainment industry. In 1986, USITT developed the DMX 512 protocol as a
simple, flexible, and reliable standard for lighting control.

In 1998, USITT transferred maintenance of the DMX 512 protocol to the Technical Standards Program of
ESTA. The standard is constantly revised and updated as technology continues to advance.

2.2 ESTA

The Entertainment Services and Technology Association (ESTA) is a non-profit trade association representing
the entertainment technology industry. ESTA promotes professionalism and growth in the industry and provides
a forum where interested parties can come together to exchange ideas and information, create standards and
recommended practices, and address issues of training and certification.

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DMX 101: A DMX 512 Handbook

2.3 ANSI

The American National Standards Institute (ANSI) is an organization composed of representatives from industry
and government that collectively determine standards for the electronics industry as well as many other fields,
such as chemical and nuclear engineering, health and safety, and construction. ANSI also represents the United
States in setting international standards. New electronic equipment and methods must undergo extensive testing
to obtain ANSI approval.

In 2004, ANSI approved the DMX 512 standard, and has since approved several other related standards
including Remote Device Management (RDM) and Architecture for Control Networks (ACN). The actual
standards are listed below:

• ANSI E1.11-2004 - Entertainment Technology USITT DMX512-A - Asynchronous Serial Digital Data
Transmission Standard for Controlling Lighting Equipment and Accessories

• ANSI E1.20 - Entertainment Technology RDM - Remote Device Management over USITT DMX512

• ANSI E1.17 - Entertainment Technology ACN – Architecture for Control Networks (Multipurpose

Network Control Protocol Suite)

2.4 EIA/TIA

The Electronics Industry Alliance (EIA) is a trade organization composed of representatives from electronics
manufacturing firms across the United States. EIA began in 1924 as the Radio Manufacturers Association
(RMA), and has grown to include manufacturers of televisions, semiconductors, computers, and networking
devices. The group sets standards for its members, helps write ANSI standards, and lobbies for legislation
favorable to growth of the computer and electronics industry.

The EIA is composed of several subgroups including the Telecommunications Industry Association (TIA). The
EIA/TIA-485 standard is the communication basis for DMX 512.

2.5 References

For more information on any of these organizations or standards, visit their websites:

• www.usitt.org

• www.esta.org

• www.ansi.org

• www.eia.org

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3. Theory of Operation

DMX 512 is an asynchronous serial digital data protocol. While that might mean something to an engineer, most
people are not familiar with how all this techno-gibberish actually accomplishes lighting control. This section
will attempt to explain how DMX operates in a simplified and easy-to-understand manner.

The topics this section will cover are:

• The Cable TV Analogy

• DMX Communications

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DMX 101: A DMX 512 Handbook

3.1 The Cable TV Analogy

A central concept of DMX 512 is the ability to transmit data on multiple channels over a single cable. To better
understand this concept, imagine a simple cable TV system (Figure 1) with four major components:

• Cable TV Company

• Cable

• Decoder

• TV

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Figure 1

The Cable TV Company broadcasts many channels at once in a mixed signal over a single cable. The Cable
carries the signal to a Decoder, usually a cable TV box or similar device. The Decoder is able to separate all the
channels from one mixed signal, and send only the desired channel to the TV (channel 001, in this example),
ignoring the rest.

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