[time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

[Eric Scace]

Another fascinating tuning-fork standard was used together with a Synchronome to govern the timing of pulses of Morse code on undersea telegraph cables in the British empire’s globe-girdling telegraph network. Timing was derived electromagnetically from incoming Morse code signals (a bi-polar signal where one polarity represented a dit and the other a dah, but both dit and dah were of equal length) to set the master at each downstream relay/switching station on a cable route.

In essence, brass, mahogany and electromagnetics were use to perform all the functions done today on fiber optic cables: signal generation, multiplexing, regeneration, and timing recovery… not to mention encoding & decoding plus printing.

One can see a working example at the Museum of Undersea Telegraphy in Porth Curno, Cornwall — a museum well worth the detour to Land’s End.

— Eric

> On 2017 Dec 09, at 10:11 , Don <dlewis6767 at austin.rr.com> wrote:
> 
> Thank you, Pete.   -Don
> 
> ==========================
> 
> 
> 
> 
> On Sat, 2017-12-09 at 05:57 -0800, Pete Lancashire wrote:
>> Here's a look at a 723-C (1,000 cps) and how its power supply cap was
>> handled and a good look inside
>> 
>> https://www.eevblog.com/forum/reviews/vintage-teardown-general-radio-
>> 723-c-vacuum-tube-tuning-fork/
>> 
>> 
>> The GR Experimenter
>> 
>> http://www.americanradiohistory.com/Archive-General-Radio/GR%20Exp%20
>> 1941_10.pdf
>> 
>> There is another Experimenter that goes into how the tuningfork was
>> made
>> but can't find it
>> 
>> -pete
>> 
>> On Sat, Dec 9, 2017 at 5:18 AM, Don <dlewis6767 at austin.rr.com> wrote:
>> 
>>> 
>>>> 
>>>> I was fortunate to find a vintage, General Radio (GR) Model 723D
>>>> Precision Oscillator (tuning fork).
>>>> 
>>>> The exceptional wooden case is as 'exciting' to look at as is the
>>>> mechanical tuning fork inside (400Hz).
>>>> 
>>>> As it is ac powered, I'll need to recap it before I turn it on.
>>>>  Then, we can test for accuracy! (sic).
>>>> 
>>>> A real class-act, 'time-nut' oscillator from the last century,
>>>> predating crystals.
>>>> 
>>>> Don
>>>> 
>>>> Don Lewis