I have put a figure below of the wiring I used to make my JP1 box. The breadboard shown is the Radio Shack solderless breadboard (276-175). All the diodes and the 22µF capacitor are shown in their proper orientations.

The only place the figure below deviates from my wiring is in the DB25 parallel connector. Here I have shown contacts 18-25 linking to a single ground connection. In my box, each contact had it's own wire connecting to a seperate ground connection. You can see that in the pictures of my box.

NOTE: The only place I deviated from the schematics was in not installing a switch (shown as SW1 in the schematics). The purpose of the switch is to change to voltage from 5V (for remotes with 4 batteries) when the switch is closed, to 3.7V (for remotes with 2 batteries) when the switch is open. Since I only have a 15-1994 remote, which has 4 batteries, I just wired this connection in the closed position (as shown by the green wire). If you want to have the option of using both types of remotes, then just replace the green wire in the diagram with a switch.

There have been several post in the JP1 newsgroup saying that the wires running to the JP1 connector should be less than 6 inches. I don't know if this is true or not, but I made mine a little less than 6 inches and it worked fine.