Attachment 453092 If your are having noise issues with your cnc machines limit switches and getting random false limit or input triggers. This filter is for you and does not matter if its wired as a parallel, or a series limit switches setup. You can build the filter as pictured. It in theory should clean up noise regardless of your voltage. Again this is a standard limit switch filter IGNORE the fact that its showing an arduino. I have now used this filter with an arduino, a planetcnc and the mach3 usb motion controller with wonderful success.