----- 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
record players, and there was a thriving industry changing these to 60Hz...
Steven C. Barr