Be careful. What Howard (lightfoot) is offering is a way to turn an old transmitter into a box that only works with simulators/PCs. It will never work as a real transmitter again. It doesn't need a buddy box hookup because you are going to throw all the electronics away.

The alternative, which is what most of us do, is to use a working transmitter which you can also use to fly your models. For that you will need a buddy socket and also a battery, charger etc. because it's a real transmitter. That's what you would want an interface for. Howards version doesn't need an interface as it plugs straight into the PC.

Both possibilites are perfectly valid but you have to decide which you're going for because they're very different.

Steve