Thanks Jazz. Have just had a NPN normally closed proximity switch delivered from Amazon. Im guessing then that with this device I would set the input for it to active high? Im going to have a play with it at the weekend. I have wired a couple of steppers and drivers up to the IPM to get them moving and to get familiar with Mach and the hardware. I'l connect the proximity switch up and see how it works. The electrics and the machine haven't come together yet.