A piece of hardware allowing a PC (or in rare cases) Mac to output DMX to control lighting. Probably the least expensive quality product is the http://www.controlbooth.com/forums/glossary/11007-enttec.html DMX USB Pro, which lists for USD 151. Other popular solutions are HES/Barco HogIII widget and MA Lighting's 2Port Node. To date, none of the tradtional lighting manufacturers (ETC, Strand, Leviton) have profferred a solution, as they are in the business of providing dedicated hardware, not free or low-cost software on a PC. While most agree that there is no substitute for a dedicated control surface, a PC solution may be appropriate in some situations.