I've seen a number of toots about knitting machines in the last year.
My first encounter with a circular knitting machine like that was as a toy from Mattel in the '70s. It was made of plastic, it was probably a little bigger than the old metal ones were. And you could use it to knit a tube. I grew tired of it soon because I didn't know how to make the tube into socks, didn't know how to make the tube into anything useful and interesting to me.