Most expression pedals have the ability to reverse the polarity of the connection to be compatible with the widest range of devices, but some of them, such as the Yamaha FC7 do not have such a switch, therefore they can only work with some instruments.
Our EX2M Adapter is designed to work with standard pedals. However, you can additionally use the TRS Polarity Adapter to make it compatible with reverse polarity pedals, such as the Yamaha FC7 or the Zoom FP02M.