This handy John Plocher design is a bench test unit for our cpOD or Bruce Chubb's DCCOD or any compatible style detector. A board is inserted into the test pins and the three buttons are pressed in sequence while observing the "detected" LED. A "good" board will light up with both the "low" and "normal" button presses, but not the "high" one. The DCCOD sensitivity can be adjusted in the jig to give the desired behavior.
A local test track can be optionally connected that enables the testing of specific locomotives and rolling stock simply by placing them on the track.
You can find detailed instructions, schematics and Gerbers (CAD files for producing your own boards) at John's website.