> On Apr 3, 2024, at 2:20 PM, Paul Koning via cctalk <[email protected]>
> wrote:
>
>
>
>> On Apr 3, 2024, at 1:49 PM, Rick Bensene via cctalk <[email protected]>
>> wrote:
>>
>> ...
>> Even with only having to render the digits zero through nine and a decimal
>> point (the calculator didn't support negative numbers; they were represented
>> using tens complement form), the display generator also used a batch of
>> diode-transistor gates to generate the digits. The interesting thing
>> about it is that instead of generating strokes to create the digits, the
>> machine uses sine/cosine waveforms that are gated by the character
>> generation logic to draw the digits on the screen. The position of the
>> digits, like the CDC scopes, is derived by precision resistor DACs, and then
>> a mixer takes over as the character is drawn using gated segments of the
>> sine and cosine waveforms mixed together with the position voltage. The
>> result is really beautifully rendered digits that look almost like they are
>> drawn by a draftsperson who is extremely consistent in the drawing of each
>> digit. The CRT has yellow-orange phosphor with a moderate persistence, so
>> when the digits change, they look like they quickly morph from one digit to
>> the next.
>>
>> The digits are among the nicest looking digits that I've ever seen on a CRT
>> display, including those on the CDC scopes as well as IBM console displays.
>
> I have, somewhere, a copy of a paper that describes analog circuits for
> generating waveforms for digits along the lines you describe. Might have
> been from MIT, in the 1950s, but right now I can't find it.
Found it (on paper): "Generating characters" by Kenneth Perry and Everett Aho,
Electronics, Jan 3, 1958, pp. 72-75.
Bitsavers has it in the MIT/LincolnLaboratory section:
https://bitsavers.org/pdf/mit/lincolnLaboratory/Perry_and_Aho_-_Generating_Characters_-_Electronics_19580103.pdf
paul
