Someday I'm going to take a photo while experimenting with DB9 connectors on the Atari Joystick ports or RS-232 ports and this box is going to be in the middle of a mess of wires. Some one is likely to ask, "What's up with that box?" This is an attempt to have this information ready to answer that very question.
If your from the future, I guess it worked.
It is simply a pass through box for each of the pins of a DB9 connector. It simply passes the signal for a pin to pin match when the header jumpers are in place. The exposed headers make it easy to read the voltages. The header pins also make it easier to wire hardware to the pins using female jumper cables.
Remove the pin jumpers on the inner two rows of the header pins and it opens up the connection between pins. Connector wires can then be used to change the pins input signals to different output pins. One such case would be to make a null modem connection.
This would be a good way to practice your soldering skills. No expensive components to burn up. The header pins should make it easy to check for solder bridges between pins. I'm glad I found the ones I created before anything was plugged into it.
2 male DB 9 connectors
2 female DB 9 connectors
8 sections of 9 header pins
16 head pin jumpers
wires (from an old joystick cable, maybe
You may want to purchase a couple of DB9 male and female gender changers. You'll know why when you need to plug a male ended cord into a male DB9 connector.