History has shown that introducing DMX as the standard control protocol was an important factor in the successful of lighting industry. It enabled creating “open architecture” systems, which meant the possibility of mixing equipment from various vendors
 
DMX was originally intended for use in linking controllers and dimmers of different manufacturers. However it soon became the primary method for linking more advanced fixtures (moving lights) and special effects devices such as foggers. One limitation of DMX is that  there is no error detection or correction in this protocol. Therefore DMX can’t be used to control pyrotechnics effects, moving stage sets truss movement equipment and basically anything that could endanger human safety by DMX control malfunction.
 
A short description of DMX:

• Developed in 1986 by USITT, revised in 1990
• Electrically   based upon EIA RS- 485 voltage levels
• Runs on shielded, twisted pair data communications cable
• Dimmer intensity information for 512 dimmers plus status byte = 0, RDM extension to DMX uses status byte # 0
• 255 steps between zero to full intensity
• Max cable length is 250 m
• Moving light fixture uses adjacent DMX channels to control their attributes
  

Each fixture connected to the DMX universe has to have an independent address set to respond to DMX control. As an example let’s take  a fixture with number of fife attributes each:

1^st channel                    -           Pan

2^nd       “                        -           Tilt

3^rd         “                       -           Dimmer

4^th         “                       -           Color

5^th         “                       -           Gobo

Let’s assume we have 4 fixtures using 5 the same DMX channels and the fixture addresses are starting from address 10.

Fixture 1 occupies channels       10 thru 14

“           2   “                  “           15 thru 19

“           3    “                 “           20 thru 24

“           4    “                 “           25 thru 29

The DMX map of attributes per fixture is:

	Fixture	Fixture	Fixture	Fixture
Attribute	1	2	3	4
Pan	10	15	20	25
Tilt	11	16	21	26
Dimmer	12	17	22	27
Color	13	18	23	28
Gobo	14	19	24	29

DMX support components:
The various configurations of DMX networks led to the development of  a number of hardware/software support components.

1. DMX tester
2. Splitter
3. Merger
4. Protocol converter
5. Demultiplexer DMX/DC

What DMX tester can do?

• Verify console output 
• Control dimmers directly
• Test DMX cable
• View DMX parameters thatcontrol moving lights
• Analyze DMX signal
• Act as a DMX flicker finder
  

What DMX tester can do?
 
Verify console output 
Control dimmers directly
Test DMX cable
View DMX parameters thatcontrol moving lights
Analyze DMX signal
Act as a DMX flicker finder
 
DMX Splitter
 
Standards require that DMX devices be installed in a daisy chain with no tees or stars in the DMX wiring. However, site conditions way make star wiring preferred oreven mandatory.DMX splitter permits star wiring by making each branch of the star appear electrically as its own entity, unaffected by other branches of the star.Additionally, opto-isolation circuitry isolates each branch to prevent ground loops or accidental damage from fault voltages on DMX lines.