I personally think it's foolhardy to think that any one particular device can give adequate copy protection. If a design engineer assumes the product is 100% safe then they deserve what they get. Perhaps there is a moral here: you only get what you pay for. Rich Department of Applied Physics, University of Hull, HU6 7RX Tel 01482 465135 Fax 01482 465606 // E-mail R.J.Smith@apphys.hull.ac.uk