Mostly true. But upstream signalling predates cable modems by a certain period; originally the upstream was intended for things such as city 'public access' st

Mostly true. But upstream signalling predates cable modems by a certain period; originally the upstream was intended for things such as city 'public access' stations to feed back to the headend (to then be transmitted back out to customers). It's existence was certainly handy for the use of cable modems.