IBM 80
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Image:Cardsorter.fhwa.jpg The IBM 80 Electric Punched Card Sorting Machine, was introduced by IBM in 1925.
This sorter was almost twice the speed of the older IBM 70 sorter and used an entirely new magnetically operated horizontal sorting design.
At the close of 1943, IBM had 10,200 of these units on rental.
The basic operation of a card sorter is to take a stack of IBM punch cards, examine a single column, and place the card into the corresponding pocket. There are twelve rows on a punch card, and thirteen pockets; one pocket is for "reject" cards.
Cards pass through the sorter with the bottom edge ("9-edge") first. A single small metal brush is positioned; as each card goes through the machine each spot in a single column passes under the brush in turn. Wherever there is a hole, the brush can make contact with metal roller underneath it; when this happens an electric circuit is formed. That circuit in turns directs the card to pass into the correct bin. This is done by slipping the card into a stack of metal strips (or chute blades) that run the length of the sorter feed mechanism. The hole detected determines where in the stack of chute blades the card is inserted. Each blade ends above one of the output pockets corresponding to the hole that was detected, and the card is deflected into the pocket. There are 13 pockets, corresponding the punches in rows Y, X, 0 throuigh 9 and a Reject pocket for cards containing no holes in the selected column.
To sort several columns, you have pass the cards through several times, moving the brush each time. Sorting is done by first sorting by the least significant digit up to the most significant digit. This is called a "bin sort".
Letters of the alphabet are indicated by two punched holes in the same column, one hole in one of the first three rows (Y, X, or 0), and the other in one of the remaining numeric rows (1-9). The first zone is letters A-I, the second is J-R, and the third S-Z. Each letter is further encoded by a numeric punch 1 through 9, in alphabetic order. The 0-1 punch is skipped in alphabetic sequence, so the Z is encoded as 0-9).
Alphabetical sorting is handled by sorting cards twice on the same column, first on rows 1-9, then on the "zone" rows Y, X, and 0. Operator switches allow zone-sorting by "switching off" rows 1-9 for the second pass of the card for each column.
Since numbers only require one punch per column, in rows 0-9, only one pass per column is required.
Other special characters and punctution marks were added to the card code, involving as many as three punches per column, but card sorters did not sort such characters appropriately.