I have read that Danish inventor Vladimir Poulson had an AC generator in 
his lab, and that was very early 20th century. Perhaps an electronic 
source for a tone was available in Edison's day, altho I would assume 
very expensive at the time.

It appears that electro-mechanical oscillators date back to the 1860s:

http://xenia.media.mit.edu/~gan/Gan/Education/NUS/Physics/MScThesis/Chapter1.html

joe salerno


On 4/15/2013 2:45 PM, Mickey Clark wrote:
> I have a similar record - except the number is  3342-B-4-? a small mark
> obscures the digit after the 4. It could be a way of establishing
> whether the governer in the Edison phonograph produced wow. Maybe a
> pantograph from a mechanical source could have provided the original
> tone e.g. mechanical in origin -not audio-Mickey
>
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> ----- Original Message ----- From: "Dan Nelson" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Sunday, April 14, 2013 10:34 PM
> Subject: Re: [ARSCLIST] Edison "tuning" disc ?
>
>
>> What in the world is this Edison "tuning disc"  #3342B21 ?
>> It sounds like 800hz tone  but they didnt have tone generators back
>> then did they?  maybe tuning fork over and over.
>> Many thanks for info on what it was for  and how it was made
>> dnw
>>
>

-- 
Joe Salerno