The polarity cannot be changed onboard the keyboard itself. Yamaha musical instruments require a "normally closed" switch pedal. The recommended pedals are the Yamaha FC4 and FC5. You can also use a Yamaha FC3 as a sustain pedal by making the Sustain Pedal setting in Utility Mode... This will allow you to take advantage of the Half Dampering feature for more realistic Sustain Pedal behavior.