Drum printer

In a characteristic drum printer design, a permanent font character set is carved onto the margin of a number of print wheel, the number corresponding the number of columns (lettering in a line) the printer can print. The wheels, connected to form a big drum (cylinder), spin at high pace and paper and an inked band are stepped (moved) past the print position. As the desired character for each column passes the print position, a hammer strike the paper from the back and press the paper against the band and the drum, causing the preferred character to be record on the continuous paper.

Since the drum haulage the letterforms (characters) remains in constant movement, the strike-and-retreat act of the hammer had to be very quick. Naturally, they were driven by voice coils mount on the moving piece of the hammer.