Stallman about surveillance

[Stewart C. Russell]

On 13-11-06 12:47 PM, James Knott wrote:
> 
> Well, it lost time, as induction motors rotate at slightly under the
> power frequency (or fraction).  This meant we had to modify some Data
> General computers that used the power line for the real time clock.

I keep having to remind myself that mains frequency makes a fairly
decent clock. The only time that I noticed it at work is when it does
something wrong.

If you ever get the chance to tour the IESO's super-secret HQ in
Oakville, they have their old Synchronome indicator clock on display.
Synchronomes - two clocks with Invar pendulums, one kept in an evacuated
vessel, signalling to the other - were the most accurate mechanical
clocks available before atomic clocks came along. The Hydro used it to
maintain grid frequency. They were stupendously expensive. Now you can
get surplus atomic clocks (Rb, not Cs, but good enough) for < $100 ...

cheers,
 Stewart
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