[time-nuts] NBS 1000 CPS Tuning Fork Standard?

[Brooke Clarke]

Hi:

Somehow I got dropped from the mailing list around March 9, but have been added back.

Hi:

I recently stumbled onto this at the Wiki page for tuning forks:
https://en.wikipedia.org/wiki/Tuning_fork#In_clocks_and_watches
Showing an NBS 1,000 CPS standard.

related to a discussion on the GreenKeys list server about the history of the tones used for radio teletype.
https://prc68.com/I/TuningForks.html#AFSK-Tones
and that lead to the NBS 1927 Yearbook pages 40 and pdf page 408
https://prc68.com/I/TuningForks.html#NBS_1000_CPS_Standard
https://www.google.com/books/edition/Standards_Yearbook/5h_9yYrnBCYC?hl=en&gbpv=0
Fig 16 (pdf pg 408) "Pendulum oscillations" and Fig 17 "Tuning-fork vibration".

Can someone explain what's shown in Fig 16 on pdf page 408?  Maybe a Shortt pendulum can sitting on a shelf off the 
stack of bricks?

-- 
Have Fun,

Brooke Clarke
https://www.PRC68.com
axioms:
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2. Everybody, with no exceptions, holds false beliefs.