Quartz movement

NIST states the general principle first: "Clocks work by counting a periodic event with a known frequency."

Then the quartz case: "With a quartz clock (like most wristwatches), a piece of quartz crystal is cut and used in an electronic circuit where it vibrates at a certain frequency (usually 32,768 Hz)." And the counting: "The frequency is 'counted' by dividing it by 32,768 to equal one second 'ticks'." NIST adds the reason this design is good: "By dividing a high frequency down to a low frequency, the accuracy can be increased."

Why 32,768 Hz. Writing in the British Horological Institute's Horological Journal, NIST's Michael Lombardi records: "The quartz watch industry standardised on 32 kHz crystals in the early 1970s due to their reliability, their compatibility with existing electronic circuits, their small dimensions, and their low power consumption." The value is 2¹⁵ Hz.

What is not claimed here. It is often said the figure was chosen because 2¹⁵ divides neatly through fifteen binary stages. That may be so; neither source says it, so this Codex does not.

The first commercial quartz wristwatch ran slower: the Seiko Museum records that the 1969 Quartz Astron used an 8,192 Hz oscillator, and "a frequency of 32,768 Hz became the standard for later quartz timepieces".