Editing IBM 407 (section)

==Description==
[[File:IBM-407-at-Nokia.jpg|thumb|IBM 407 (left) with [[IBM 519]] (on right).]]
The 407 read [[punched card]]s, 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 [[plugboard|control panel]] and a [[carriage tape]].  Exit hubs (impulse emitting) on the control panel are wired to entry hubs (impulse accepting) for the task to be done (see [[Plugboard#Wiring of unit record equipment|Wiring of unit record equipment]]).  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, say in invoice number, totals could be printed. Unlike [[Tabulating machine#Models and timeline|earlier IBM tabulating machines]], which had 80 read brushes at each read station, one for each column, the 407 had 960 brushes at each station, one for each possible hole in a punched card. Cards were held in position during each read cycle and the per digit pulses needed were generated using [[Commutator (electric)|commutators]], one for each column. This allowed the card to be read more than once at each station, for greater flexibility.<ref>{{cite web |url= http://www.bitsavers.org/pdf/ibm/punchedCard/Training/A24-1007-1_IBM_Functional_Wiring_Principles_Feb66.pdf |archiveurl=https://web.archive.org/web/20110219021336/http://www.bitsavers.org/pdf/ibm/punchedCard/Training/A24-1007-1_IBM_Functional_Wiring_Principles_Feb66.pdf |archivedate= February 19, 2011 |title= IBM Functional Wiring Principles |publisher= IBM |date= February 1966}}</ref>

For printing, the 407 used type wheels, an improvement over earlier tabulators that used print bars. The 48-character wheels were stationary until a character impulse was to be printed; the wheel then rotated in two steps. the first step rotated each wheel to one of 12 groups of characters based on the digit impulse associated with that print position. Digit impulses included the digits 1 through 9 (in reverse order), the 8-3 and 8-4 combination punches and a group (N) for no digit impulse. One of four characters in each group was then selected based on the zone impulse (0, 11, 12 or none) for that character position. This selection happened at the same time the type wheel was driven against the ribbon. The timing of the zone impulse selection was controlled by a complex set of linkages and electromagnets called the Analyzer, one for each of the 120 print positions. Each type wheel also emitted an impulse (called "echo") for the character actually printed.  The control panel could be wired so the echo impulses were accumulated for totals; report totals then reliably reflected what had actually been printed.

Mechanical systems including the card reader, printer, counters and storage units were all driven by a single motor, which also drove an oil pump and a generator that provided 46-volt power for the  electrical logic. This included about 900 [[relay]]s which were mounted on three swing-out gates. The control panel had a matrix of 43 by 52 holes, most of which were assigned.

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.