IBM 407

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A 407 at U.S. Army's Redstone Arsenal in 1961.

The IBM 407 Accounting Machine, introduced in 1949, was the culmination of a long line of IBM tabulating machines dating back to the days of Herman Hollerith (see the tabulators and accounting machines in List of IBM products#Unit record equipment). It was the central component of any unit record equipment shop. In the late 1950s, the 407 was adapted as an input/output device on early computers, such as the IBM 650. Later, 407 print mechanisms were used in the IBM 1132 line printer, part of the low cost IBM 1130 computer system.

The 407 read punched cards, totaled fields on the cards, made simple decisions, printed results, and, with the aid of a summary punch, output results on punched cards that could be input to other processing steps.

The operation of the 407 was directed by the use of a removable control panel. Exit hubs (impulse emitting) on the control panel are wired to entry hubs (impulse accepting) for the task to be done (see photos). There are hubs for each card column (at both reading stations), print position, counter digit, and so on. Logic tests were also available.

Each input card was read at two successive reading stations. Thus, for example, fields in a card could be compared with the following card and, should a change be detected, totals printed. For printing, the 407 used wheels, an improvement over earlier tabulators that used print bars. The wheels were stationary until a character impulse was to be printed; the wheel then rotated to one of 47 positions for printing, was driven against the platen, and then emitted an impulse (called "echo") for the character actually printed. The control panel would be wired so the echo impluses were accumulated for totals; report totals then reliably reflected what had actually been printed.

The 407 was available in a model that could read 100 cards per minute, and one reading 150 cards per minute. The former had a relay which would inhibit every third card feed cycle (giving the machine a characteristic "shrink-shrink-thunk" sound). It was possible to insert a folded card between that relay's contacts to "overclock" the slower model to the faster speed.