It looks like a regular line printer where the drum keeps spinning. See wikipedia:
>Because the drum carrying the letterforms (characters) remains in constant motion, the strike-and-retreat action of the hammers has to be very fast. https://en.wikipedia.org/wiki/Line_printer
>Because the drum carrying the letterforms (characters) remains in constant motion, the strike-and-retreat action of the hammers has to be very fast. https://en.wikipedia.org/wiki/Line_printer