Andy, >It's interesting to see how many opinions there are on what the Regs mean about certain scenarios.< This means that the Regs are badly written! Any standard that leads to discussion as to what it means is, de facto, badly written. As a cynic, I'll add that I expect little else from the Society of Electricians (which is what the IEE was called before it was the Telegraph Engineers) I'll add that I've done my share of standard writing at ETSI - officially, the European Telecommunciations Standards Institute, and unofficially, the European Travel and Sightseeing Institution!! Peter Chadwick Swindon MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.