IR repeater

I was wondering if any one had built one or knows of a design on the net. It seems to me one can be built for less than Niles or Xantrek want. I want to be able to control my system while I'm in another zone. All I need is an in out device, I'll use the system remote. Any ideas?

Thanks for the site info. I built it the other night, it didn't work at first. If any one else wants to build one here are a few changes that need to be made.The layout shows a 3904 transistor it should be 3906 since the IR module drops voltage when IR is detected. Also the 150k resistor that helps set the 40khz carrier needs to be about 190k to get some gear to respond. (With the 150k only my Adcom and Sony stuff would respond when changed to 190K it all worked Marantz, Panasonic, JVC and Home Brew.) It can be built for about 25 dollars which is much cheaper than Xantech, etc.