4. Cabling
Every DMX fixture is fitted with an input and output to interface with the chain. These connectors are typically XLR sockets (either 3 or 5 pin). DMX is designed to be daisy-chained. Therefore only one output is needed from the lighting desk and is sent through all fixtures in series.
Simple DMX chain
Luckily it’s not necessary to follow a certain order of devices as the signal is not altered in anyway throughout the chain. You can run the DMX cables the way, it’s practical for you. Let’s say you addressed a fog machine as your first device on the DMX Master, nevertheless it could be placed at the End of your DMX chain.
Although the 3 pin XLR connectors are used in audio equipment as well, the actual strands differ in detail. While microphone cables are designed for analog signals in the kHz range, DMX cables carry a digital signal in the MHz range. In practice it usually doesn’t throw any problems if a microphone cable is used for small setups or testing fixtures but we recommend the usage of a proper DMX cable as for the mentioned reasons.
The DMX output of the last fixture should be terminated with a defined resistance of 120 ohms. Such an end plug is called “DMX-Terminator”. Not doing so could result in signal reflections, making it difficult for the fixtures to decode the DMX Signal properly and behave unexpectedly.
Additionally every fixture needs its power supply. Conveniently many offer the feature of having a power out socket. Therfore they can throughput mains power via the matching link cables.
