"Switching mode power supplies, particularly in their isolated form, fill a niche which has arisen, for example, with the developement of 'add on' units such as vcr's and hi-fi sound, games, etc. in TV receivers. In some parts of the world, e.g. Australia, isolation is mandatory for safety reasons"the part "fill a niche which has arisen" caught my eye. it implies that these are specialized solutions to specific issues, not "just another" p/s topology. Sam