[cctalk] Re: oscilloscopes

On Apr 3, 2024, at 1:49 PM, Rick Bensene via cctalk <cctalk(a)classiccmp.org> 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.