Lights
A red light at the door, status lights on the projector
Lights show what holds right now: a blink(1) as the red light at the studio door, light boards as status lights for every person at the table, on a second screen or a projector.
blink(1)
ThingM's USB light with two LEDs, mk2 and mk3: off, glow, blink, pulse and colour sequences. Anything that moves the device plays itself, evenly and without the Mac's help. Stagehand reads back what it shows and switches it off when quitting, so no red light burns with nobody behind it.
Light boards
Lights without a device, in a window of their own: columns side by side, say one per person, and in each the same lights one above the other, say mute and wants to speak. The window keeps its shape, can be dragged to another screen and switched to full screen, light or dark.