And those buttons needed to be round, because you could turn them to tune the radio or TV to a station. Pressing the button would then "snap" the tuner back to the preset position of the pressed button.
Ok, apparently there were different ways this was implemented. I remember a friends old TV as a child, where it worked exactly as I have described.
This is similar to what I mean, although it's a radio, not a TV and the buttons I remember where taller and had ridges on the side so they could be turned easily.
I think turning the tuning knob typically popped out the preset button, and holding the button down while turning the tuning knob changed the preset. I think this could be done with a loop of string (to control where the dial arrow was) and few springs and catches (to pull the string into position when the button was pressed).
I can’t imagine how the mechanism would work if each preset knob was a tuning knob.
There was only one knob. To set a preset, you first pull the button out towards you, which released sort of a clamp internal to the mechanism, then push the button back in, and it would clamp on the string at the new position.
I'm gonna have to shoot a video next time I'm at my parents' place, aren't I? (The old Blaupunkt still serves as a stereo in the garage.)
This is similar to what I mean, although it's a radio, not a TV and the buttons I remember where taller and had ridges on the side so they could be turned easily.
https://herculodge.typepad.com/herculodge/2011/06/as-i-walke...