The Handsonic HPD-20 has a footswitch input jack (FOOT SW) on the back panel, which lets you connect up to two external footswitches to control various parameters.
Note: Footswitches connected to the FOOT SW jack cannot be used to trigger sounds.
The following are compatible footswitches.
To assign a function to a footswitch, press [MENU] → "SYS" → "FootSw Control" → "Foot Switch 1" or "Foot Switch 2," then use the VALUE dial to select the desired function.
For details on connection methods and settings, refer to "Using a Footswitch (FOOT SW)" in the HPD-20 Owner's Manual.