The 'Sustain' and 'Foot Switch' jacks on the rear panel of the S80 are made to be used with a Yamaha FC-4 Sustain Pedal or FC-5 Foot Switch.

Due to the fact that some manufacturer's sustain pedals and/or foot switches are configured differently than the Yamaha FC-4 and FC-5, the sustain (or some other parameter) may work backwards, or not at all.

NOTE: The 'Sustain' jack is used for sustain only, however the function of the 'Foot Switch' jack is programmable.