I bought a boss FS-5L footswitch for my roland cube amp and does what it is supposed to do, but i found i have to press the switch twice to change the channel. I was wondering if this was normal because i thought you just press it and it switches. And also it has a polarity switch and ive been looking around for a while and i kinda understand what that means but i just want to make sure what that is, because people have said things like youll fry this or that if you dont have the polarity right. Thanks in advance for help.