Few people have heard of it, yet many consider John Blankenbaker's KENBAK-1 to be the first commercial personal computer.
The Oscilloscope Clock
By James Grahame
I seem to be one of the last three people on Earth who prefers basking in the luminescent glow of a good old cathode ray tube (actually, two of them). That makes me the perfect customer for a CRT-based clock.
The Scope Clock is another of David Forbes' nifty electronic timepieces (we mentioned his Nixie watch in December). It's based on a 3-inch round CRT with "a crystal-controlled microcontroller
for generating the timing and scanning the digits, and an analog circle generator
system to draw the digits. It makes circles directly from sine and cosine waves.
That's why the curves look so clean.
The drawing of the digits is done in segments, each segment being composed of an arc,
circle or line. Angled lines are made by putting the same cosine wave onto both
the X and Y deflection plates.
The display repetition rate is synchronized to the power line frequency by the
microprocessor to prevent image 'swimming' in the presence of strong AC fields.
This allows the CRT to be free of magnetic shielding, which would add to the cost
and detract from the beauty of the clock."
