How does a screen work?

When I learned how TV worked at the beginning of television history, I found it super cool that the camera and all the TVs across the country had their scanning beams synchronized. That camera was driving your TV, almost literally.

I only recently found out that the tech to save images wasn’t invented, so they couldn’t display a revolving logo between shows. So… so the BBC had a permanent real-life logo with a permanent camera in front of it.

So yes, any image was extremely ephemeral at the time.

PS: Apparently it’s called a Noddy, it’s a video camera controlled by a servomotor to pan and tilt (or 'nod', hence the name Noddy): https://en.wikipedia.org/wiki/Noddy_(camera)

I don’t think that was why the Noddy was used. At the time film and projection were available. They could have recorded film and projected onto a sensor for re-broadcast.

The Noddy was used since it was a live broadcast and “allowed the idents to be of no fixed length as the clock symbols could continue for many minutes at a time”.

So, it’s not really because they couldn’t store video. It’s because they needed an indefinite amount of video for the clock idents and couldn’t generate them digitally.

Film wears out through repeated use. While a loop of film would have been theoretically possible, the tech to transmit it would have required just as much TV camera electronic equipment, plus a complex film projection device; the film would have gradually gotten scratched and picked up dust and worn out, and it would have had a great many failure modes.

In contrast, pointing a TV camera at a spinning globe was much easier. And for showing the time, pointing at a physical clock was much easier than, what, having twelve hours of film footage available and having to synch the right frame?

I think what’s maybe more surprising for people than that moving station idents were typically in camera props, is that broadcasting even a static image pre-digital was also much more easily accomplished by just pointing a camera at a piece of card - even repeating a single frame over and over again was not something that could be easily reproduced some other way; having a camera continually capture and immediately broadcast the frame was just much easier.

Video tape, once it came in, allowed freeze frames but continually reading from the same spot on a tape caused wear so you couldn’t rely on being able to show a single frame from tape indefinitely.

Digital freeze frame machines that could capture a frame of video and repeatedly play it back from a memory buffer only started showing up in the 1980s.