It's easy! As long as your devices are being run in a domain where their behaviour is purely, well, digital, one can get away with it! :-) I'm a perfect case in point! I seem to have some bizarre brain dysfunction where I have a very hard time understanding even the simplest analog circuits. You, or someone like Brent Hilpert (whose explanation of core memory drivers I still remember :-) can explain something with sufficient clarity for me to 'get' it, but I can almost never work it out on my own. However, I've designed a number of digital devices, at least one of which became a product! Noel