DISCLAIMER: There is a possibility you can screw up or burn out your parallel port if you do things wrong! I AM IN NO WAY RESPONSIBLE FOR WHAT YOU DO TO YOUR COMPUTER/PARALLEL-PORT AND WILL NOT BE HELD ACCOUNTABLE FOR ANY DAMAGE YOU MAY CAUSE. Use this advice at your own risk.

If you've got gportal installed you'll probably need to build some kind of interface for your parallel port so you can do useful things like turning on/off lights. This page will explain some of the basic concepts and circuits.

Tools you'll need are wire strippers/cutters, a soldering gun/iron and an electronic meter for testing. It would also be handy to have some sort of numbered marking tape so you'll know which wire is which. You'll also need some basic knowledge of electronics and an ability to build simple circuits.

First thing you'll need is something to plug into your parallel port. This can be either a printer cable or a DB25 plug. If you are using a printer cable you'll need to cut off one end (the end that doesn't plug into your port). Then strip away some of the insulation to get at the wires, say about 3 inches/8 cm. If you're using a DB25 plug you'll need enough wire to hookup 8 pins plus a ground. It doesn't have to be very thick wire as the voltages/currents are pretty minimal.

The pins you want for switches are 2 through 9 and the ground pins are 18 through 25. If you're not sure which is which you'll need to use your meter while running gportal. Turn on Switch 1 and find Pin 2 and any of the ground pins. Do the same for the rest as needed and mark your cable or DB25 plug.

The jpeg below has the basic circuit which you'll need to duplicate for each pin. It should suffice for most common applications. The circuit shows a 12v source, if you use relays that have a different voltage you'll need to adjust for them and possibly change the 2N2222A transistor. Except for the cost of the relays everything else shouldn't cost more than a few dollars.

If you do a web search you can find out more about printer port pin layouts as well as probably find other circuits you can use.