Paper tape punch
The write half of paper tape: a row of solenoids driving holes through paper faster than the eye can follow, and a box that fills up with confetti.
A punch has eight punch pins per character position plus one for the sprocket track, each fired by a solenoid when its bit is meant to be a one. Underneath sits the chad box, which somebody has to remember to empty — a full box jams the pins and produces wrong characters in the middle of a program listing.
Punches are strikingly slow compared with readers. The Teletype ASR-33's built-in punch managed ten characters a second, a standalone Teletype BRPE around a hundred, while an optical reader could take a thousand. That asymmetry shaped how the medium was used: tape was punched once and read many times. The chadless variant cut a hinged flap that stayed in the hole, so text could be printed legibly along the tape — handy for humans, useless for optical readers, and a neat illustration of how one small mechanical choice decides what equipment can read your media.