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Using the electric utility frequency for timekeeping — How accurate is it?

The Analog-Style LED Clock uses the 50 or 60Hz from the electric utility as a time base to keep accurate time without the use of a crystal oscillator. The clock automatically detects whether it is connected to 50 or 60Hz and adjusts accordingly.  A question I’m often asked is “How accurate is the electric utility frequency?” The short answer is that it is surprisingly accurate.

In the 1920’s Laurens Hammond invented an electric clock driven by a synchronous AC motor. It kept time using a motor that was in sync with the 60Hz frequency generated by the utility companies. He gave away hundreds of these clocks to power stations as an incentive to maintain a steady frequency which allowed his inexpensive clock to be used anywhere in North America. Hammond went on to help create the Hammond Organ which used a synchronous AC motor to drive a “tone wheel” generator which created perfect pitches for the organ.

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