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----- Original Message ----- >>>>> From: Richard L. Hess If you used a 60Hz machine on 50Hz mains, then the tape recorded at the following speeds will play back at the second speed in the pair: Nominal Actual 1.88 1.57 3.75 3.13 7.50 6.25 15 12.50 30 25.00 This requires a machine that can shift downward by 16.7% Repeating the same exercise, but with a 50Hz record machine run on 60Hz mains, you get Nominal Actual 1.88 2.26 3.75 4.50 7.5 9.00 15 18.00 30 36.00 This requires a machine that can shift upwards by 20% <<<<< This gets me to wondering...were tape recorders being sold in Toronto before much of Ontario was changed from 25 to 60 Hz? I know there are 25Hz electric clocks and record players, and there was a thriving industry changing these to 60Hz... Steven C. Barr