Many thanks for the replies. Just to confirm I have not experienced this before and as I said the layout was operating perfectly,,,,,,,well may be not perfect! At switch on yesterday the problem became apparrent. I do use a CDU, the buzz is only when a point is operated. All running track sections work fine apart [of course] from sections supplied by a point which wont move!!!
Should I try disconnecting the selection switches in turn?
Again thanks for your interest and time.