DMX512 is the language consoles use to talk to fixtures. One universe carries exactly 512 channels, each a value from 0–255. A simple dimmer uses one channel; a moving head can use 30 or more.
Address + footprint
Every fixture has a start address and a footprint (how many consecutive channels its current mode uses). A fixture at address 100 in a 16-channel mode occupies channels 100–115. The next fixture must start at 116 or later — if it starts inside that range, the two overlap and fight for control.
When you run out of room
A 16-channel fixture can't start above 497 (497 + 16 − 1 = 512). When a universe fills up, you move to the next one. Networked protocols carry many universes over Ethernet:
- Art-Net — universes addressed as net / sub-net / universe.
- sACN (E1.31) — universes 1–63999, priority-aware, the modern default.
8-bit vs 16-bit, and reading a patch sheet
Resolution: a single DMX channel has 256 steps (0–255). For a slow pan that is too coarse — you would see stepping. So fine attributes use a pair of channels (coarse + fine) giving 65,536 steps. That is why an "extended" fixture mode has a bigger footprint: it is spending channels on resolution.
Reading a patch sheet: each row maps console channel → DMX start address → universe → fixture and mode. If two rows share overlapping address ranges in the same universe, that is a clash to fix before the fixtures ever power on.