---snip--- Contrary to what Tom Jennings states in a later post, there are sound physical reasons for using fractional systems when dealing with the physical world. I'm not defending the English system that is a hodgepodge of poorly related measurement standards. The only reason we have a decimal system is because of the number of fingers we have. Hardly a sound reason to squeeze physical relations into. One wonders why there are 2.5mm screws when the decimal system works so well. If we'd had 8 finger, things would have been so much easier to work with. 8 is 2 cubed and one hand would be 4 or 2 squared. These both fit nicely into the physical world were squares cubes are most often worked with. Even logs would have made more sense under a base 8 system. I've been trying to find some actual history on the 50/60 thing on the net but so far, all I was able to find was that cell phones are frying our brains. My understanding was that it was a balance between efficient generation and efficient transformers. The voltages were mainly to control line loss. In the US, most people live close to their distribution transformer and line loss is not that high at 110-115V. Dwight