TV’s from the 80’s and 90’s definitely weren’t digitizing incoming video and generating graphics. So how did they overlay things like the channel, volume, and menus?
In: Technology
The analog television signals use brief voltage dips, to signal the horizontal sync and vertical sync of the image. It’s very cheap and easy to use simple ’80s and ’90s circuits to detect the sync pulses and then precisely time a semiconductor switch to choose: whether the original analog video signal or digitally-generated analog color signal will be displayed at any part of the screen.
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