Copyright 1998 Doug Fleenor Design, Inc.
DMX 512 A: Simple Explanation
Here's what DMX512 was intended to do
The end of a DMX512 signal must be terminated so the signal cycle can begin again.
Some Limitations of the Original DMX512 Specification
- All devices on a DMX512 link are connected in a daisy chain. The output of one feeds the input of the next.
- A cable failure anywhere on the link can bring the entire system down. An AC fault in one of the dimmers
can blow every piece of equipment on the DMX512 link: console, scrollers, fogger, etc.
- Depending on product design, as few as five devices may overload the consoles ability to drive the system.
Optically Isolated Splitters solve some of the DMX512 Problems
- Optically isolated splitters were invented to overcome some of the limitations of DMX512. A cable failure on one output cannot affect the devices on another output.
- A well designed splitter will protect against an AC fault in one of the dimmers causing damage to other equipment.
- Data errors caused by a faulty device on one link will not affect the data integrity on the other outputs.
- Some splitters have "thru" connectors. These should be used only when connecting one splitter to another with a short jumper cable. If not used, they must be terminated.
- Each output of the splitter can drive many devices.
- Just as the console can drive up to 1000' of 120 Ohm data cable, so can each output of a splitter.
- Unused outputs of the splitter do not need to be terminated.
Optically Isolated Splitters Solving Some More Challenges