For those who just want to buy one that's been done right you should be able to get one for $20-$25 at a theater dealer (Yes that is about three times the price of doing it yourself). Doug Fleenor makes one that has a LED that shows you are getting good DMX signal, and spike suppression built in for about $50... that could be really hand to have at the long end of a run (see your dealer for pricing).
As for learning what this DMX thing is all about and why you need termination. The book "Practicle DMX" will be the best $30 you've ever spent.
As for learning what this DMX thing is all about and why you need termination. The book "Practicle DMX" will be the best $30 you've ever spent.