Back in the early 80's I became the owner of an IBM light pen, IIRC salvaged from a 3270 terminal. By replacing the connector, I managed to get it to work with the CGA card in my IBM PC, which had a light pen connector and a couple of supporting registers.
When the pen was clicked against the screen, it notified the card when it saw the scanline, in a manner quite similar to the duck hunt gun described here. The position of the pen click could then be read from a register on the card.
When the pen was clicked against the screen, it notified the card when it saw the scanline, in a manner quite similar to the duck hunt gun described here. The position of the pen click could then be read from a register on the card.