Hi all!  Douglas K. Rhodes, in MMD 00.07.22, brings to mind another
possibility that may have influenced the early phonograph and
gramophone recording system designs.

Some time ago, before 1930 I think, the power in Los Angeles and
probably elsewhere was 50 cycles per second (50 Hertz) (and in Canada
25 Hz?).

At the Wiltern Theatre in Los Angeles (1962) the pipe organ blower
had a belt-driven 10-volt DC generator, with a label affixed by the
Los Angeles Water and Power Department, saying, "This unit converted
to 60 cycles" -- the only 60 Hz DC generator I have ever seen!  :)

In 1945 I was given a photographic dark-room timer that was 50 cps.
I had to convert every time to its 60 Hz equivalent.  My Spencer Turbine
Company organ blower (1925) is labeled 50 Hz.

I understand that 100 volts was also common at some point in the past.

John Spradley
Sylmar, CA

 [ Long Beach CA changed from 50 Hz to 60 Hz in 1948, I believe.
 [ A contractor was hired by the city water and power department
 [ to exchange all the synchronous electric clocks in the city.
 [ The city thought that the old clocks would be discarded, but the
 [ shrewd contractor then sold the 50 Hz clocks in South America!
 [ -- Robbie