DMX-512 is a widely adopted, open standard. It carries 512 8 bit dimmer channels over an RS-485 serial link.

DMX was ratified, I believe around 1990. At the time many vendors had already developed their own solutions to the 'giant console cable' problem. Over time, DMX won out, even for 'intelligent' fixtures, but many vendors, like NSI, still support their own protocols as well as DMX.

The advantage to the company is clear - if you have a proprietary control link, you are pretty much forced to stick with compatible dimming, etc., from the same company. The advantage to the user varies. In the case of NSI, I would argue that it is none. Microplex carries fewer channels (128? 192? something like that), and is no more reliable than DMX.

MA offers extra features, like status reports and custom dimming curves, when you use their proprietary dimmer link. But, still, I think most users are better off going with DMX and keeping their vendor options wide open.

-jjf