[burnte]

The TV syncs to the clock in the input signal that the console generates. The console knows what line the TV was on because it's the line that the console is currently outputting. Analog TVs were very simple devices where the signal coming in via the wire or antenna was basically pumped directly to the CRT to manipulate the beam. While at the user's end it looked like a raster, it's all analog tricks.

Imagine a text file pushed out theough a serial port, all the data is just dumped on to the wire and the other end worries about interpreting carriage returns and line feeds. You just imagined how old line printers worked!

When the TV wasn't able to figure out the sync signal you'd get rolling [1] or tearing [2] where the picture was being displayed the best the TV could make out.

1: https://youtu.be/bGXEqzCS4nE?t=28 2: https://www.youtube.com/watch?v=FVOVk3psy-w