Chances are you may have a different image than what Gibson had since the way a dead channel appears on a CRT had changed over the years and Gibson had mentioned that he was thinking of some very old TVs from his childhood. Here is a relevant thread on scifi stackexchange including a video of a TV from the era Gibson described:
But in practice i think everyone would understand even without seeing it the first time - it is like phonographs/gramophones, most people nowadays haven't used one in real life but they do know how they look like.
https://scifi.stackexchange.com/questions/163304/what-color-...
But in practice i think everyone would understand even without seeing it the first time - it is like phonographs/gramophones, most people nowadays haven't used one in real life but they do know how they look like.