This is an 8 bit serial
protocol used primarily to control stage equipment: rigging, lights, smoke machines
and almost any incidental equipment that can be controlled digitally.
DMX-512 is RS485 serial at 250 Kbaud--much faster than MIDI's 31.25 Kbaud. Owing to the much broader spectrum of tools, cheaper cabling, and probable concurrent use of MIDI anyway, MIDI Show Control is also a popular protocol.
www.yale.edu/dramat/sound/showcon.html has a very nice history of show control protocols.