Punched cards contained information (programs and data). This information was fed into the computer via the input unit called card reader. The card reader is composed of a read hopper containing the punched cards to be read and a receiving hopper where read cards are stored.

A popular type of read station used brushes. This system is equipped with a drum. The drum has the same number of electrically isolated sections as the card has tracks. There is the same number of brushes as tracks. An electrical impulse is generated whenever the brush makes contact with the drum through a hole in the card.

The brushes and drum were replaced by a set of photoelectric cells in other systems.