Light Pens ...

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Mon Jul 16 17:16:39 2001

On slower systems when the light pen is pressed against the screen (or a
button is pressed) the screen would "flash" which was the video circuit
sending one frame of 'white' so that the pen would detect it. This is how
the old console displays on the System/370 worked (god would I love to have
one of those to play with) Other systems would light up a single row (move
it down through the frame) which was less intrusive visually. There are
other ways to make it work but basically without light eventually hitting
the sensor you were stuck.
--Chuck

At 02:01 PM 7/16/01 -0700, you wrote:
>Ok, my mind is still blown. How does a light-pen drawing program work
>then? (Or is a light-pen drawing program not possible?)
Received on Mon Jul 16 2001 - 17:16:39 BST