A friend of mine wanted to shed light on a stage, and (dimming) control the lights with the computer. There are now inexpensive DMX 4 channel switch pack under 100 €, so you can head 4 spots. However, DMX-512 PC interface cards can be expensive and relatively rare in a laptop install. I have devised a simple circuit with only two small ICs that can solve this problem.
The RS-232 Converter =⇒ DMX 512 can not only control DMX dimmers, but all devices Who have a DMX512 connection.