User manual

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5. APPENDIX

A Quick Lesson On DMX

DMX(akaDMX-512)wascreatedin1986bytheUnitedStatesInsti-

tute for Theatre Technology (USITT) as a standardized method for con-

necting lighting consoles to lighting dimmer modules. It was revised in

1990andagainin2000toallowmoreexibility.TheEntertainment

ServicesandTechnologyAssociation(ESTA)hassinceassumedcontrol

over the DMX512 standard. It has also been approved and recognized

forANSIstandardclassication.

DMX covers (and is an abbreviation for) Digital MultipleXed signals. It

is the most common communications standard used by lighting and

relatedstageequipment.

DMXprovidesupto512control“channels”perdatalink.Eachofthese

channels was originally intended to control lamp dimmer levels. You

can think of it as 512 faders on a lighting console, connected to 512

lightbulbs.Eachslider’spositionissentoverthedatalinkasan8-bit

number having a value between 0 and 255. The value 0 corresponds to

the light bulb being completely off while 255 corresponds to the light

bulb being fully on.

DMXdataistransmittedat250,000bitspersecondusingtheRS-485

transmission standard over two wires. As with microphone cables, a

grounded cable shield is used to prevent interference with other sig-

nals.

TherearevepinsonaDMXconnector:awireforground(cable

shield), two wires for “Primary” communication which goes from a DMX

source to a DMX receiver, and two wires for a “Secondary” communica-

tion which goes from a DMX receiver back to a DMX source. Generally,

the“Secondary”channelisnotusedsodataowsonlyfromsources

to receivers. Hence, most of us are most familiar with DMX-512 as

being employer over typical 3-pin “mic cables,” although this does not

conformtothedenedstandard.