Cable was built for controlling the Canon 10D shutter using DSLR Focus by Chris Venter as per instructions on his site. The cable connects to the computer's parallel port. As an electrical engineer, I had most of the parts needed on hand. I had to buy the Canon RS80N3 for the needed proprietary N3 connector.
For the male parallel port connector I cut one off an old cable that had a plastic AMP connector hood. I mounted a 1/8" (female) stereo jack on the side of it to accept a 20 foot Headphone Extension Cord that I bought from Radio Shack for $8 (#RS42-2562) . There was enough room in the connector hood for the two resistors, two transistors and the stereo jack. I did not use a perf board but instead covered soldered connections with shrink wrap.
I cut the Canon RS80N3 remote cable in half and installed a 1/8 inch male stereo phone plug on the N3 connector side and installed a 1/8 inch female in-line phone jack on the RS80N3 hand control side. With this arrangement I can use the RS80N3 in its short original configuration or for a longer reach with the 20 foot extension cable. The 20 foot extension cable can be used with the short N3 connector cable and the parallel port connector for DSLR Focus control with a computer.
At Radio Shack I also bought a Y-adapter Cable for $5.49 (#RS42-2496). It is the white cable in the photo below and allows control of the Canon 10D shutter manually with the RS80N3 hand controller and also by computer using DSLR Focus at the same time.