Chain printer
A line printer whose characters ride a horizontal chain looping past a bank of hammers.
In a chain printer a steel band of cast characters runs in an endless loop, sweeping horizontally past the paper at speed. Behind the paper sits one hammer per column; when the glyph a column needs happens to pass by, the hammer fires and presses paper and ribbon against it. Because each character appears several times around the chain, no column waits long for its turn.
IBM made the design famous in the 1403 (1959), which later moved to a stiffer "train" where the slugs slid in a track rather than on a link. The scheme was faster and more durable than the older drum printer and produced straighter lines, since a character's vertical position no longer depended on exact rotational timing. Swappable chains let one machine print different character sets.