I got myself this harmony effects unit recently, just to have a bit of fun with but also to encourage me to actually learn to sing in tune.
It works great but I wanted to use a foot switch with it so it can sit on the keyboard and I can operate it with my foot. T.C Helicon have a couple of such switches but research indicates that neither is currently available and probably won’t be for a while.
Some digging around revealed that the DigiTech Fs3X pedal would probably work. At this web site I found the following diagram for such a switch.
And then on Diyguitarist.com I found this pdf that described the FS3X wiring (reproduced here, copyrights acknowledged):
This just confirmed they were the same so I felt safe plugging the FS3X into the Harmony-M and sure enough it works great. Even better, I managed to get the FS3X from the local Guitar Center for $15 vs the mid thirties price I was seeing online. The sales guy did have to go digging in the stock room for it though but hey, I couldn’t even buy the parts to make my own for that.