There are several different designs for interfaces, some are boxes, some are just cables, but they can all be found in the "Interfaces" folder in the file section at Yahoo Groups. As time permits, I will include some of the designs here on this site along with part numbers.
The only design you really need is the Simple Interface which is by far the easiest to build, the others are included here for reference purposes, these are older designs than the Simple one.
"Simple" Design (by Tommy Tyler)
"Micro Perf" Design (by Tommy Tyler)
"Classic" Design (by Dan Nelson)
"Remote powered" Design (by Tommy Tyler)
Opening Up The Remote
Here's a link to the folder at Yahoo Groups: