IBM 80 series Card Sorters

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Later model IBM card sorter, type 84

Card Sorters in the IBM 80 series were:

IBM 80 Electric Punched Card Sorting Machine Introduced by IBM in 1925. This sorter was almost twice the speed of the older Hollerith 70 vertical 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.
IBM 81 Sorter
IBM 82 Sorter Sorted cards at 650/minute.
IBM 83 Sorter Sorted cards at 1000/minute (photo).
IBM 84 Sorter Sorted cards at 2000/minute.

The basic operation of a card sorter is to take a punched card, examine a single column, and place the card into the corresponding pocket. There are twelve rows on a punch card, and thirteen pockets in the sorter; one sorter pocket is for "reject" cards (without a punch or sorter feed errors).

Cards pass through the sorter face down with the bottom edge ("9-edge") first. A single small metal brush or optical sensor is positioned so that, as each card goes through the sorter, a single column passes under the brush or optical sensor. When a hole in that column is detected, an electric circuit is formed, directing the card to the correct pocket. 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.

Multiple column sorting is done by first sorting the least significant column, then proceeding, column by column, to the most significant column. This is called a least significant digit radix sort.

Numbers have one punch per column in rows 0-9; a numeric column can be sorted in a single pass through the sorter.

Letters of the alphabet are indicated by two punches in the same column, one hole in one of the first three rows, called zones, (12, 11, 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 (0-1 is skipped, S is 0-2 and so on to Z, 0-9).

Alphabetical sorting is handled by sorting cards twice on the same column, first on rows 1-9, then on the "zone" rows 12, 11, and 0. Operator switches allow zone-sorting by "switching off" rows 1-9 for the second pass of the card for each column.

Other special characters and punctuation marks were added to the card code, involving as many as three punches per column (and in 1964 with the introduction of EBCDIC as many as six punches per column), but card sorters did not sort such characters appropriately.