RJ45 jumper box

This is a small circuit board that allows you to prototype arbitrary RJ45 cables / pin-outs. Once the pin-out is confirmed, you can go ahead and crimp a cable with matching pin-out, having verified that it is correct.

laforge finds this very useful, particularly in the context of the many different RS232 on RJ45 pin-outs in use by various equipment out there.

Hardware v2

In the hardware version v2, the PCB design was switched to a two-layer design, and both RJ45 connectors are now located on the top side of the PCB. This significantly increases the usability.

Hardware v1

This is a single-layer PCB design. In order to make the PCB routing easy, the RJ45 connectors are on opposite sides of the PCB.

Design files

The PCB design files are available at


It's OSHW, so you can build it yourself based on our design files published above. If you prefer a fully assembled product, sysmocom is offering fully assembled kits in their webshop at

Updated by laforge 10 months ago · 5 revisions

Add picture from clipboard (Maximum size: 48.8 MB)