Comment by CableNinja

Sega was also the pioneer of online gaming, in a sense. SEGA channel was a service provided by your cable company. You got an adapter that went into your SEGA and had a coax that went to your tv box. Every month you get access to 20-40 games, all of which were a range of titles everyone could enjoy. There was no multiplayer, except locally. You could even plug in games you owned without removing the adapter. Also had the bonus of the ability to play the sonic version with the red sonic, by plugging in one of your sonic versions, when the adapter had the red sonic game expander available in its game list.

To me it still holds as one of the coolest technologies (aside from a computer of course) from my childhood. Managed through tv channel sideband data.

https://en.wikipedia.org/wiki/Sega_Channel