Susan Kline asked:
> Am I correct in thinking that the top note of the dial tone is always 440?
That is true in many parts of the US, but not all. There are many rural phone systems that utilize different kinds of dial tones. It would be interesting to have those on the list with access to an ETD to measure the A in their dial tone and report back here.
The only A440 I know of that is guaranteed to be accurate is the one on shortwave radio station WWV and available over the phone by calling 303-499-7111 in Colorado. But keep in mind this 440 Hz tone is only available for 45 seconds each hour, starting at exactly 2 minutes after the hour.
Robert Scott
Ypsilanti, Michigan
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