Don't forget how they found a way to squish closed caption information into analog broadcast. The electron beam traces a path on the CRT display by drawing the odd lines from top to bottom (which draws half the image) and then the even lines (the rest of the owl) from top to bottom. While the electron beam is repositioning itself from the bottom of the screen to the top of the screen, there is a brief period of time where other data can be transmitted. That's where closed caption data was shoehorned in.