If a secondary data pair is used, a termination resistor is connected across it as well. A terminator is a stand-alone male connector with an integral 120 Ω resistor connected across the primary data signal pair this resistor matches the cable's characteristic impedance.
The specification requires a 'terminator' to be connected to the final OUT or THRU connector of the last slave on the daisy chain, which would otherwise be unconnected. For example, the block diagram below shows a simple network consisting of a controller and three slaves. A second cable then links the OUT or THRU connector of the first slave to the IN connector of the next slave in the chain, and so on. The controller, which usually has only an OUT connector, is connected via a DMX512 cable to the IN connector of the first slave. For example, a lighting console is frequently employed as the controller for a network of slave devices such as dimmers, fog machines and intelligent lights.Įach slave device has a DMX512 "IN" connector and usually an "OUT" (or "THRU") connector as well.
A network consists of a single DMX512 controller – which is the master of the network - and one or more slave devices. It was revised again in 2008, and is the current standard known as "E1.11 – 2008, USITT DMX512-A", or just "DMX512-A".Ī DMX512 network employs a multi-drop bus topology with nodes strung together in what is commonly called a daisy chain.
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The resulting revised standard, known officially as "Entertainment Technology-USITT DMX512-A-Asynchronous Serial Digital Data Transmission Standard for Controlling Lighting Equipment and Accessories", was approved by the American National Standards Institute (ANSI) in November 2004. In 1998 the Entertainment Services and Technology Association (ESTA) began a revision process to develop the standard as an ANSI standard. False triggering may be caused by electromagnetic interference, static electricity discharges, improper cable termination, excessively long cables, or poor quality cables.ĭeveloped by the Engineering Commission of United States Institute for Theatre Technology (USITT), the DMX512 standard (for Digital Multiplex with 512 pieces of information ) was created in 1986, with subsequent revisions in 1990 leading to USITT DMX512/1990. However, it is still used for such applications. DMX512 does not include automatic error checking and correction, and therefore is not an appropriate control for hazardous applications, such as pyrotechnics or movement of theatrical rigging. It can now be used to control almost anything, reflecting its popularity in all types of venues.ĭMX512 uses a unidirectional EIA-485 (RS-485) differential signaling at its physical layer, in conjunction with a variable-size, packet-based communication protocol. It quickly became the primary method for linking controllers (such as a lighting console) to dimmers and special effects devices such as fog machines and intelligent lights.ĭMX512 has also expanded to uses in non-theatrical interior and architectural lighting, at scales ranging from strings of Christmas lights to electronic billboards and stadium or arena concerts. It was originally intended as a standardized method for controlling stage lighting dimmers, which, prior to DMX512, had employed various incompatible proprietary protocols. It allows a DMX universe from one source to be repeated to several chains of devices, in order to avoid signal degradation due to long cable runs.ĭMX512 is a standard for digital communication networks that are commonly used to control lighting and effects.