The rig stays lit after Stop or Quit

You press Stop, or close LMS, and the fixtures stay stuck on whatever they were showing. This confuses people into thinking the software is still running.

Why it happens

DMX and its network descendants are stateless streams. A fixture does not receive "off" — it receives a continuous stream of levels, and if that stream stops it simply keeps displaying the last frame it received. Some fixtures time out to black after a few seconds; plenty do not, and hold the last look indefinitely.

So "the software stopped sending" and "the software told everything to go dark" are completely different things, and only the second one actually turns the rig off.

What LMS does

On Stop and on Quit, LMS runs a blackout sweep — it explicitly sends a frame of zeros to every enabled output before it stops sending or shuts down.

⚠ This matters when a new output type is added: if it is not wired into that sweep, rigs on that output will hold their last look forever. Serial DMX was missed once for exactly this reason and the symptom was baffling until someone realised only that one output was affected.

If your rig still stays lit

1. Check the output is actually enabled in LMS — the sweep can only clear
outputs it knows about.
2. Quit properly rather than killing the process. If LMS is force-quit or
the machine loses power, nothing gets a chance to send the blackout.
3. Some controllers latch. A few Art-Net nodes hold their last frame even
after receiving zeros, and need a power cycle or their own blackout setting.

Related: why a DMX line must keep flowing

The mirror image of this: a DMX line has to keep sending continuously, even when nothing is changing. Receivers time out to black if the stream stops. That is why LMS keeps transmitting every tick rather than only sending when something changes — an optimisation that seems obviously sensible and produces dark fixtures.