Swap low connecton

[tonyjohnson]

I am wiring my plane to be able to swap radios from COM1 to COM2 and visa versa with a button on the stick. I am using an infinty stick grip. The chinese hat switch, left position will be used. That is a momentary button with a ground wire and signal wire.

The PS engineering PMA 8000B audio panel pin 20 on connector J2 is for "swap" pin 21 is "swap low".

It seems reasonably clear that the wire from the infinity grip button should go to the audio panel pin 20 (swap). What connects to pin 21 (swap low)?

Any help would be appreciated.