When I was a kid in the '80s, we had a Magnavox TV with built-in Pong. The game mode button was at the top of the side panel with the VHF and UHF knobs. Blue and Red controllers plugged into the back of the set, each with a rotary encoder and trigger.
Edit: Just found an image of the same one https://i.redd.it/kzvv4pq6f1h21.jpg