223:. Thus an impulse that occurred during 7-time on a wire connected to the column 26 punch magnet would punch a hole in row 7 of column 26. An impulse on the same wire that occurred at 4-time would punch a 4 in column 26. Impulses timed in this way often came from read brushes that detected holes punched in cards as they passed under the brushes, but such pulses were also emitted by other circuits, such as counter outputs. Zone impulses and digit impulses were both needed for alphanumeric printing. They could both be sent on a single wire, then separated out by
38:
49:
173:
182:
110:
393:
428:
412:'s workings. Plugboard wirings were part of the "day settings" that specified which rotors to insert into which slot, and which plugboard connections to make. In practice the plugboard did improve the security of the cypher being generated, but as it did not change with every keypress, unlike the rotors, its impact was limited.
125:, Otto Schäffler invented the plugboard in order to easily reprogram tabulators. Applications then could be wired on separate control panels, and inserted into tabulators as needed. Removable control panels came to be used in all unit record machines where the machine's use for different applications required rewiring.
332:
that position. Emitters might be used to put a numeric constant value, say a date, on every card. Alphanumeric constant data could be created by carefully combining digit and zone pulses. Later machines, such as the 407 also had a complete set of alphanumeric emitters that only required one wire to use.
354:
had a D entry hub that caused the selector magnet to pick up on the next machine cycle, and X entry hub that also delayed but was only triggered by an 11 or 12 pulse. The one-cycle delay was needed because in most cases, by the time a pulse was detected it was too late to reliably take action in that
313:
Simple comparing circuits had two entries and one exit that emitted a pulse whenever pulses arrived at the entries at different times. Some machines, e.g. collators, could detect which number was higher if they were not equal. A tabulating machine might compare the account number on successive cards
205:
would advance from one station to the next, a line might be printed, a total might be printed and so on. The cycles were divided into points according to when the rows on a punched card would appear under a read or punch station. On most machines, cards were fed face down, 9-edge (bottom edge) first.
192:
Unit record equipment was typically configured for a specific task using a removable control panel. The electrical connections of the various components in the unit record machine were presented on the panel, and connections between them were determined by the wiring, with the actual connections made
279:
entries to specify either addition (plus) or subtraction (minus). If neither were pulsed, no operation was performed. If addition was commanded, a digit impulse wired from a column to a counter entry hub started the counter wheel turning. It stopped automatically at zero time. Thus a pulse at 8 time
188:, such as this, were widely used in unit record equipment. When current flows through electromagnet, 1, the iron armature, 2, is pulled in, pivoting on a bearing at its corner (not shown) to move the common contact, 3. A relay can have more than one set of contacts. Co-selector relays had five sets.
140:
at each end of a single-conductor patch cord were inserted into hubs, making a connection between two contacts on the machine when the control panel was placed in the machine, thereby connecting an emitting hub to an accepting or entry hub. For example, in a card duplicator application a card column
144:
Tabulator functions were implemented with both mechanical and electrical components. Control panels simplified the changing of electrical connections for different applications, but changing most tabulator's use still required mechanical changes. The IBM 407 was the first IBM tabulator that did not
90:
The contacts on the machine are hard wired to the various devices that comprise the machine, such as relays, counters, inputs from each card reader column, outputs to a card punch column or printer position, and so on. The wiring on a plugboard connects these devices to perform a specific function,
369:
were similar to emitters, with one exit hub for each cycle point, but they also had an entry hub that was switched to the successive exit hubs as the cycle progressed. A digit selector could be converted to a digit emitter by wiring its entry hub to a constant source of cycle pulses. But it could
213:
pressed against the card, one for each column (the 407 read station, constructed without brushes, held the card stationary and could read a card multiple times, each time generating the same impulses as would be generated by an 80 spring wire station). When a hole passed under the brush, the brush
331:
were sets of 12 exit hubs that automatically generated a pulse at each specified time in the card cycle. The twelve exit hubs were wired to contacts on a rotary switch that turned with the card cycle. Thus wiring the 6 exit from an emitter to a punch magnet entry would cause a 6 to be punched at
267:
one hub for each print position. Impulses to these entries controlled the motion of print bars or wheels to place the correct type element under the print hammers. The 407 also had exits from each print wheel that could then feed the counters for addition or subtraction. This insured that totals
370:
also be fed other signals and used to detect a particular digit. Wiring a first read brush to a digit selector's entry and connecting, say, its 4 exit to a pilot selector's D entry would cause that selector to transfer on the next read cycle if a 4 was punched in that first read brush's column.
318:
using opposing electromagnets. If neither magnet was energized or both magnets were energized at the same time, the relay armature would not move. If only one magnet was energized, the armature would move and touch one of two contacts placed on either side. The two contacts were wired together
302:
hub caused that counter to emit total pulses which could be wired to print positions. After a total was printed, the counter was reset. Special circuits allowed negative values to be printed correctly, not as nines complements, and a special exit was provided to allow an appropriate symbol
176:
An 80-column punched card. Rows 0 to 9 are labeled. The 12 row, on top, has one punch in column 7. The 11 row, below it is not punched on this card. As cards passed through a read station, usually 9-edge (bottom edge) first, wire brushes, one for each column, would make contact through the
141:
reading (emitting) hub might be connected to a punch magnet entry hub. It was a relatively simple matter to copy some fields, perhaps to different columns, and ignore other columns by suitable wiring. Tabulator control panels could require dozens of patch cords for some applications.
382:
Later machines such as the 407 and 602 could store several values for later use, by means of a mechanical device somewhat similar to an emitter, except it contained a sliding contact that determined at what time point an impulse was to be emitted. The contact slider was positioned
218:
in IBM terminology, would be generated. Each brush was connected to an individual hub on the control panel, from which it could be wired to another hub, as needed. The action caused by an impulse on a wire depended on when in the cycle it occurred, a simple form of
200:
Wiring a unit record control panel required knowledge of the machine's components and their timing constraints. The components of most unit record machines were synchronized to a rotating shaft. One rotation represented a single machine cycle, during which
274:
An IBM tabulating machine, such as the 402 or 407 series would have several counters available in different sizes. (For example, the IBM 402/403 had four sets each of 2, 4, 6 and 8 digit counters, labeled 2A, 2B, 2C, 2D, 4A, 4B etc.) Each counter had two
439:
computer was programmed via cabling, switches and plugboards. ENIAC's cabling was later reconfigured to use the existing
Function Tables data ROM memory as program ROM memory (the switches and plugboards continued to be used in the reconfigured ENIAC).
245:
The capabilities and sophistication of unit record machine components evolved over the first half of the 20th century and were often specific to the needs of a particular machine type. The following hub groupings were typical of later IBM machines:
609:
Early IBM removable control panels had an array of sockets on one side, each socket wired to a connector on the reverse side. As the function of such panels is identical to the later control panels with hubs, this article uses only the hub
87:. The array of holes is often contained in a flat removable panel that can be inserted into a machine and pressed against an array of contacts. This allows the machine to be quickly switched between different applications.
253:
80 exit hubs, one for each card column. A tabulating machine might have two or three read stations, each with its own set of 80 hubs. A reproducing punch might have an additional read station after the punch station for
260:
Machines that could punch cards, such as a reproducing punch, had hub entries for each card column. An impulse to one of those entries triggered the electromagnet that initiated the punching of a hole at that column
447:
used a plugboard for all program compare operations and all branch operations. Other plugboards controlled card reading and punching, the printer and the console typewriter. Many peripheral devices, e.g. the
206:
Thus the first point in a card cycle would 9-time, the second 8 time and so on to 0-time. The times from 9 to 0 were known as digits. These would be followed by 11 time and 12 time, also known as zones.
400:) on the Enigma is positioned at the front of the machine, below the keys. In the photograph, two pairs of letters are swapped (S-O and J-A). Up to 13 letters can be swapped this way.
234:
would be connected, allowing more than one wire to be connected to that exit or entry. A few groups of hubs were wired together but not connected to any internal circuits. These
145:
require such mechanical changes; all the 407's functions were electrically controlled and were completely specified by the application's control panel and carriage tape.
778:
716:
Proceedings of the
December 8-10, 1954, eastern joint computer conference: Design and application of small digital computers on - AIEE-IRE '54 (Eastern)
230:
The control panel for each machine type presented exit (output) and entry (input) hubs in logical arrangements. In many places, two or more adjacent
152:, IBM manuals describe the control panel as "directing" or "automatic operation was obtained by...". The control panels of calculators, such as the
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704:
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731:
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would make contact with a conductive surface beneath the card that was connected to an electrical power source and an electrical pulse, an
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magnet was energized. Many types of selectors were employed that differed in how the "pickup" relay was energized. In the simplest case,
648:
500:, a British manufacturer of unit record equipment that used a removable "connection-box" with mechanical linkages instead of a plug board
350:(I) entries, the magnet was energized when a pulse was received and held for the remainder of the cycle. More complex selectors, called
242:
were also available to join three or four wires together, above the control panel. Several are visible in the photo of an IBM 402 panel.
280:
caused the wheel to advance 8 steps, adding the value 8 to that counter position. Carries within a group were performed automatically.
30:
This article is about plugboards, or control panels, in unit record machines, cypher machines and early computers. For other uses, see
758:
52:
Reverse side of the same 402 plugboard, showing the pins that make contact with the machine's internal wiring. The holes were called
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80:
768:
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hubs allowed counters to be coupled, permitting longer numbers to be accumulated. Subtraction was more complicated and used
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and print a total when a new account number appeared. For the compare function, IBM implemented what would now be called a
197:, where a fixed number of logic components are made available and their interconnection wiring is determined by the user.
194:
92:
84:
689:, Wiley, 494pp. Well written descriptions of unit record machines and control panel wiring, both IBM and Remington Rand.
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missile, which feature a plugboard programmed by inserting small ferrite rods into slots, in effect creating a read-only
619:
Note: A major exception were reproducers (514...) and interpreters (552 ...), which took cards 12 edge (top edge) first.
416:
31:
220:
376:
were relays that energized during only at 11 and 12-time, allowing digit pulses to be separated from zone pulses.
75:
can be inserted to complete an electrical circuit. Control panels are sometimes used to direct the operation of
325:
allowed an output pulse to be wired to more than one input without creating a back circuit between the inputs.
91:
say reading cards and summing up the numbers punched in a group of columns. A modern comparison would be a
193:
when the panel was inserted into the machine and locked in place. Perhaps the closest modern analog is the
359:
had only an immediate input, but five sets of contacts and were typically triggered by a pilot selector's
668:
503:
122:
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76:
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IBM removable control panels ranged in size from 6 1/4" by 10 3/4" (for machines such as the IBM 077,
37:
48:
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electro-mechanically when a value was stored, and stayed in position until the storage was cleared.
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136:) to roughly one to two feet (300 to 600 mm) on a side and had a rectangular array of hubs.
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accounting machine control panel wiring. This board was labeled "profit & loss summary."
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Plugboards remained in use in specialty-purpose computers for some time, acting as a
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95:(FPGA), with the plugboard serving the same purpose as the wiring layer in the FPGA.
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408:; it was not removable. In this case the plugboard acted as a "fourth rotor" in the
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could be used to connect multiple wires when needed. Small connector blocks called
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480:
224:
72:
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internally and connected to an exit hub that indicated an unequal comparison.
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471:(ROM) but able to be manually reprogrammed in the field. One example is the
427:
148:
For most machines with control panels, from collators, interpreters, to the
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The earliest machines were hardwired for specific applications. Inspired by
17:
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IBM Punched Card Data
Processing Equipment: Functional Wiring Principles
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453:
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41:
511:, the term for a solderless plugboard used for prototyping electronics
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Punched-Card
Systems and the Early Information Explosion, 1880–1945
160:, that specified a sequence of operations, were described as being
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IBM Accounting
Machine: 402, 403 and 419 Principles of Operation
456:, for first and second generation IBM computers, including the
67:(the term used depends on the application area) is an array of
464:, were based on unit record machines and included plugboards.
307:
or "-") to be printed next to the number when it was negative.
700:
Columbia
University Computing History: IBM Control Panels
117:
Accounting
Machine Another panel is on the floor nearby.
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entry to either of two outputs, depending on whether a
685:
Brooks Jr., Frederick P.; Iverson, Kenneth E. (1963)
582:. Johns Hopkins University Press. pp. 128–137.
632:IBM Reference Manual: Functional Wiring Principles
562:Computer prehistory and history in central Europe
565:. National Computer Conference. Vienna, Austria.
168:Wiring of unit record equipment control panels
113:An operator inserting a control panel into an
8:
543:IBM Reference Manual 407 Accounting Machine
209:In a read station, a set of 80 spring wire
71:or sockets (often called hubs) into which
27:Control panel using electrical patch cords
705:IBM Archives: IBM 407 control panel photo
520:
779:Computer-related introductions in 1906
7:
404:A plugboard was used on the famous
227:based on the time within a cycle.
25:
649:IBM 305 RAMAC Manual of Operation
268:always matched what was printed.
576:Heide, Lars (April 27, 2009).
1:
195:field-programmable gate array
93:field-programmable gate array
764:UNIVAC unit record equipment
718:. ACM Press. pp. 4–11.
667:. 22-6275-0. Archived from
417:Cryptanalysis of the Enigma
795:
712:"Why not try a plugboard?"
221:time-division multiplexing
102:
29:
759:IBM unit record equipment
687:Automatic Data Processing
435:The first version of the
338:directed a pulse from a
724:10.1145/1455270.1455272
774:Cryptographic hardware
475:computer, used on the
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123:telephone switchboards
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769:Unit record equipment
504:Telephone switchboard
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105:Unit record equipment
99:Unit record equipment
77:unit record equipment
51:
40:
296:Counter total exits.
458:IBM 700/7000 series
431:ENIAC wiring panels
710:Rice, Rex (1954).
477:Bristol Bloodhound
433:
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119:
57:
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733:978-1-4503-7855-0
545:. 1959. A24-1011.
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531:. 1949. 22-5654.
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469:read only memory
363:hence the names.
352:pilot selectors,
290:nines complement
272:Counter entries.
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367:Digit selectors
277:counter control
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81:cipher machines
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103:Main article:
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676:. Retrieved
669:the original
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658:IBM (1956).
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638:. 22-6275-0.
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629:IBM (1956).
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610:terminology.
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593:. Retrieved
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481:core memory
300:Total entry
292:arithmetic.
240:wire splits
73:patch cords
753:Categories
678:2007-11-06
516:References
509:Breadboard
311:Comparing.
32:Plug board
18:Plug-board
483:by hand.
348:immediate
336:Selectors
286:carry out
261:position.
61:plugboard
742:17341809
595:19 March
559:(1976).
487:See also
460:and the
380:Storage.
329:Emitters
316:XOR gate
282:Carry in
236:bus hubs
162:programs
462:IBM 650
450:IBM 711
355:cycle.
216:impulse
211:brushes
158:IBM 604
154:IBM 602
150:IBM 407
134:IBM 514
130:IBM 550
115:IBM 407
42:IBM 402
740:
730:
586:
340:common
186:Relays
177:holes.
83:, and
738:S2CID
672:(PDF)
665:(PDF)
636:(PDF)
437:ENIAC
344:relay
138:Plugs
69:jacks
54:hubs.
728:ISBN
597:2024
584:ISBN
452:and
443:The
305:"cr"
284:and
156:and
720:doi
454:716
414:See
63:or
755::
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726:.
714:.
419:.
164:.
132:,
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744:.
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681:.
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303:(
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