I am wiring some limit switches to one of my machines (as well as an e-stop) and I noticed in the Mach2 documentation that he shows the use of a "pull up" resistor in the circuit. What is this for? I just wired my switches in with acitive hi logic and they are normaly closed; so when I trip the switch it breaks the circuit to ground and then it's 4.8V at the pin and I've got my active hi signal. What is the need for the resistor?