The connection of a mechanical switch to 1/4 stereo jack of HX 3 expander
is shown in pic
You must use a 3 way switch with middle switch position
( Humbucker switch at guitars ie )
When the " ring " is connected permanently to GND the function is only
fast slow
If the "ring" is not connected to GND the function is STOP.
So one half of the double switch is used for the stop function and the other for the
Fast - Slow function