Currently it uses two 3.5mm TRS jacks that each have three contacts: tip, ring, and sleeve. The switch bridges either the tip or the ring to ground, triggering a keyboard command. If either of these is shorted to ground at boot, that pin is ignored.
- tip - for typical stereo jacks this is the left channel; as wired this is yellow
- ring - for typical stereo jacks this is the right channel; as wired this is red
- sleeve - for typical stereo jacks this is ground; as wired this is black
- document the board wiring.