As with the drum printer, as the correct character passed by each column, a hammer was fired from behind the paper.
From the en.wikipedia.org
In a laser or LED printer, modulated light is projected onto the drum surface to create the latent image.
From the en.wikipedia.org
In drum printers, a drum carries the entire character set of the printer repeated in each column that is to be printed.
From the en.wikipedia.org
In order to transfer the ink to the sheet of paper, the printer includes a large internal drum, which is rotated at a high speed.
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Over time, the belt that moves the drum may stretch, or other mechanical problems occur, however solid ink printers contain a fraction of the moving parts that a conventional laser printer does.