DMX 101: A DMX 512 Handbook
While 4000 feet may be specified by the standard, most manufacturers recommend DMX runs of no more than 1000 feet (300 feet between devices) before using a repeater to regenerate the signal. Each device should have input and output connectors, but these are usually wired together. No re-transmission or amplification is performed.
Devices are connected in a daisy-chain fashion, from the controller to device #1, then device #1 to device #2, and so on. The final device in the daisy-chain must be terminated. The terminator absorbs signal power which would otherwise be reflected back into the cable and degrade the data. A terminator simply places a 110-120 Ohm, 0.5 Watt resistor across the two transmission wires.
NOTE: DMX cannot be split reliably by making Y-cables or T-connectors. DMX splitter/repeaters (such as the Elation Opto Branch 4) typically use optical isolation to protect each segment from electrical faults on other branches. These can be used to increase the number of devices on one network beyond the limit of 32. Each branch of a splitter/repeater can support up to 32 devices.
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