Monday, January 10, 2011

Keyboard technology

There are many types of keyboards, usually differentiated by the switch technology employed in their operation. Since there are so many switches needed (usually about 80-110) and because they have to be highly reliable, this usually defines the keyboard (Dell XPS M1210 Battery) .

The choice of switch technology affects key response (the positive feedback that a key has been pressed) and travel (the distance needed to push the key to enter a character reliably). Newer models use hybrids of various technologies to achieve greater cost savings (Dell Studio XPS 1340 Battery) .

Membrane keyboard

There are two types of membrane-based keyboards: Flat-panel membrane keyboards and full-travel membrane keyboards:

Flat-panel membrane keyboards are most often found on appliances like microwave ovens or photocopiers (Dell Studio XPS 1640 Battery) .

A common design consists of three layers. The top layer (and the one the user touches) has the labels printed on its front and conductive stripes printed on the back. Under this it has a spacer layer, which holds the front and back layer apart so that they do not normally make electrical contact (Dell Studio XPS 1640 Battery) .

The back layer has conductive stripes printed perpendicularly to those of the front layer. When placed together, the stripes form a grid. When the user pushes down at a particular position, their finger pushes the front layer down through the spacer layer to close a circuit at one of the intersections of the grid (Dell Vostro 1710 Battery) .

This indicates to the computer or keyboard control processor that a particular button has been pressed.

Generally, flat-panel membrane keyboards do not have much of a "feel", so many machines which use them issue a beep or flash a light when the key is pressed (Dell KM958 battery) .

They are often used in harsh environments where water or leak proofing is desirable. Although used in the early days of the personal computer (on the ZX80, ZX81 and Atari 400), they have been supplanted by the more tactile dome and mechanical switch keyboards (Sony VGP-BPS13 battery) .

However, membrane keyboards with interchangeable key layouts, such as the IntelliKeys and Discover:board are still commonly used by people with physical,visual, or cognitive disabilities as well as people who require assistive technology to access a computer.

Full-travel membrane-based keyboards are the most common computer keyboards today (Sony VGP-BPS13/B battery) .

They have one-piece plastic keytop/switch plungers which press down on a membrane to actuate a contact in an electrical switch matrix.

Dome-switch keyboard

Dome switch keyboards are a hybrid of flat-panel membrane and mechanical keyboards (Sony VGP-BPS13/S battery) .

They bring two circuit board traces together under a rubber or silicone keypad using either metal "dome" switches or polyester formed domes. The metal dome switches are formed pieces of stainless steel that, when compressed, give the user a crisp, positive tactile feedback (Sony VGP-BPS13A/B battery) .

These metal types of dome switches are very common, are usually reliable to over 5 million cycles, and can be plated in either nickel, silver or gold. The rubber dome switches, most commonly referred to as polydomes, are formed polyester domes where the inside bubble is coated in graphite (Sony VGP-BPS13B/B battery) .

While polydomes are typically cheaper than metal domes, they lack the crisp snap of the metal domes, and usually have a lower life specification. Polydomes are considered very quiet, but purists tend to find them "mushy" because the collapsing dome does not provide as much positive response as metal domes (Sony VGP-BPL9 battery) .

For either metal or polydomes, when a key is pressed, it collapses the dome, which connects the two circuit traces and completes the connection to enter the character. The pattern on the PC board is often gold-plated.

Both are common switch technologies used in mass market keyboards today (Sony VGP-BPS13B/B battery) .

This type of switch technology happens to be most commonly used in handheld controllers, mobile phones, automotive, consumer electronics and medical devices. Dome switch keyboards are also called direct-switch keyboards.

Scissor-switch keyboard

A special case of the computer keyboard dome-switch is the scissor-switch Sony VGP-BPL15 battery .

The keys are attached to the keyboard via two plastic pieces that interlock in a "scissor"-like fashion, and snap to the keyboard and the key. It still uses rubber domes, but a special plastic 'scissors' mechanism links the keycap to a plunger that depresses the rubber dome with a much shorter travel than the typical rubber dome keyboard Dell Inspiron E1505 battery .

Typically scissor-switch keyboards also employ 3-layer membranes as the electrical component of the switch. These stabilizing scissor-like devices extend the lifespan of the membrane to as much as 10 million keystrokes. They also usually have a shorter total key travel distance (2 mm instead of 3.5 – 4 mm for standard dome-switch keyswitches) Dell Latitude E6400 battery .

This type of keyswitch is often found on the built-in keyboards on laptops and keyboards marketed as 'low-profile'. These keyboards are generally quiet and the keys require little force to press.

Scissor-switch keyboards are typically slightly more expensive HP Pavilion dv6000 Battery .

They are harder to clean (due to the limited movement of the keys and their multiple attachment points) but also less likely to get debris in them as the gaps between the keys are often less (as there is no need for extra room to allow for the 'wiggle' in the key as you would find on a membrane keyboard) SONY VAIO VGN-FZ Battery .

Capacitive keyboard

In this type of keyboard, pressing the key changes the capacitance of a pattern of capacitor pads. Unlike "dome switch" keyboards, the pattern consists of two D-shaped capacitor pads for each switch, printed on a printed circuit board (PC board) and covered by a thin, insulating film of soldermask which plays the role of a dielectric SONY VAIO VGN-FZ18 Battery .

The mechanism of capacitive switches is very simple, compared to mechanical ones. Its movable part is ended with a flat foam element (of dimensions near to a tablet of Aspirin) finished with aluminium foil below. The opposite side of the switch is a PC board with the capacitor pads SONY VAIO VGN-FZ180E Battery .

When a key is pressed, the foil tightly clings to the surface of the PC board, forming a daisy chain of two capacitors between contact pads and itself separated with thin soldermask, and thus "shorting" the contact pads with an easily detectable drop of capacitive reactance between them SONY VAIO VGN-FZ220E Battery .

Usually this permits a pulse or pulse train to be sensed. The keys do not need to be fully pressed to be fired on, which enables some typists to work faster.

As of 2008 they are a rare find in generic PC keyboards SONY VAIO VGN-FZ340E Battery .

Vintage PCs may in some cases be equipped with this type of keyboard, because the original IBM keyboards for the Personal Computer, Personal Computer XT, and Personal Computer AT were Model F keyboards, which used the buckling spring mechanism to actuate a capacitative switch SONY VAIO VGN-FZ430E Battery ,

unlike the 101-key Enhanced Keyboard, also known as the Model M, which also had the buckling spring mechanism, but a membrane contact switch. At the present time, the best-known keyboard for use with desktop personal computers that uses a capacitative switch is that made by Topre SONY VAIO VGN-FZ460E Battery ,

either under its own name, or for Fujitsu, which sells a keyboard custom-manufactured for it to its specifications as the Happy Hacking Keyboard. The Topre mechanism uses a spring underneath a rubber dome, and the depression of the spring causes a change in capacitance between the underlying capacitor pads SONY VAIO VGN-FZ480E Battery .

There are also industrial makes of flat-panel capacitive keyboards that are inexpensive, and they resist wear, water, foreign objects and dirt.

Mechanical-switch keyboard

Mechanical-switch keyboards use real switches, one under each key SONY VAIO VGN-FZ4000 Battery .

Depending on the construction of the switch, these keyboards have varying responses and travel times. Notable keyboards utilizing this technology are the Apple Extended Keyboard (the original and/or the "II"), as well as its modern imitator, the Matias Tactile Pro. These two keyboards use ALPS switches SONY VAIO VGN-FZ31E Battery .

On PCs, the OmniKey series from Northgate Computers was popular and the line is now carried by Creative Vision Technologies under the Avant brand. Cherry Corporation of Germany also makes mechanical switches used in special purpose and high end keyboards SONY VAIO VGN-FZ31B Battery .

Their popular MX series of keyswitches are available in three actuation force/travel designs, often referred to by the colour of the centre stem to which the keycap attaches: black is a linear feel where the force increases monotonically as the key is pressed, brown provides tactile feedback as the force required decreases just before the key actuates SONY VAIO VGN-FZ31J Battery ,

and blue which is tactile and also has a click sound. In India, the TVS Gold mechanical keyboard is very popular despite costing about five times as much as a membrane keyboard.

Buckling-spring keyboard

Many typists prefer buckling-spring keyboards SONY VAIO VGN-FZ31M Battery .

The buckling spring mechanism (expired U.S. Patent 4,118,611) atop the switch is responsible for the tactile and aural response of the keyboard. This mechanism controls a small hammer that strikes a capacitive or membrane switch.

In 1993, two years after spawning Lexmark, IBM transferred its keyboard operations to the daughter company SONY VAIO VGN-FZ31Z Battery .

New Model M keyboards continued to be manufactured for IBM by Lexmark until 1996, when Unicomp purchased the keyboard technology.

Today, new buckling-spring keyboards are manufactured by Unicomp. Unicomp also repairs old IBM and Lexmark keyboards SONY VAIO VGN-FZ38M Battery .

Hall-effect keyboard

Hall effect keyboards use magnets and Hall effect sensors instead of an actual switch. When a key is depressed, it moves a magnet, which is detected by the solid-state sensor. These keyboards are extremely reliable, and are able to accept millions of keystrokes before failing SONY VGP-BPS8 Battery .

They are used for ultra-high reliability applications, in locations like nuclear powerplants or aircraft cockpits. They are also sometimes used in industrial environments. These keyboards can be easily made totally waterproof. They also resist large amounts of dust and contaminants SONY VGP-BPS13 Battery .

Because a magnet and sensor is required for each key, as well as custom control electronics, they are very expensive.

Laser keyboard

A laser projection device approximately the size of a computer mouse projects the outline of keyboard keys onto a flat surface, such as a table or desk SONY VGP-BPS13/S Battery .

This type of keyboard is portable enough to be easily used with PDAs and cellphones, and many models have retractable cords and wireless capabilities. However, sudden or accidental disruption of the laser will register unwanted keystrokes. Also, if the laser malfunctions SONY VGP-BPS13A/B Battery ,

the whole unit becomes useless, unlike conventional keyboards which can be used even if a variety of parts (such as the keycaps) are removed. This type of keyboard can be frustrating to use since it is susceptible to errors, even in the course of normal typing, and its complete lack of tactile feedback makes it even less user-friendly than the cheapest membrane keyboards SONY VGP-BPS13B/B Battery .

Roll-up keyboard

Some keyboards are designed out of flexible materials that can roll up in a moderately tight bundle. Normally the external materials are either silicone or polyurethane SONY VGP-BPS13A/S Battery .

It is important to note that although many manufacturers claim that the keyboards are foldable, they cannot be folded without damaging the membrane that holds the circuitry. Typically they are completely sealed in rubber, making them watertight like membrane keyboards SONY VGP-BPS13AS Battery .

Like membrane keyboards, they are reported to be very hard to get used to, as there is little tactile feedback.

As of 2005, roll-up keyboards include:

the CoolMac keyboard ,

the Eumax keyboard,

the VIK ("virtually indestructible keyboard") Dell Inspiron 1320n Battery ,

the pocket VIK ,

the Flexboard keyboard ,

the CoolMIR keyboard , and

the Whitelite FX100 Keyboard Dell Inspiron 1464 Battery .

Optical keyboard technology

Also known as photo-optical keyboard, light responsive keyboard, photo-electric keyboard and optical key actuation detection technology Dell Inspiron 1564 Battery .

The optical keyboard technology has been introduced in 1962 by Harley E. Kelchner – for use in a typewriter machine with the purpose of reducing the noise generating by actuating the typewriter keys.

An optical keyboard technology utilizes light-emitting devices and photo sensors to optically detect actuated keys Dell Inspiron 1764 Battery .

Most commonly the emitters and sensors are located in the perimeter, mounted on a small PCB. The light is directed from side to side of the keyboard interior and it can only be blocked by the actuated keys. Most optical keyboards require at least 2 beams (most commonly vertical beam and horizontal beam) to determine the actuated key Dell Studio 1450 Battery .

Some optical keyboards use a special key structure that blocks the light in a certain pattern, allowing only one beam per row of keys (most commonly horizontal beam) Dell Studio 1457 Battery .

The mechanism of the optical keyboard is very simple – a light beam is sent from the emitter to the receiving sensor, the actuated key blocks, reflects, refracts or otherwise interacts with the beam, resulting in an identified key Dell Latitude D610 Battery .

Some earlier optical keyboards were limited in their structure and required special casing to block external light, no multi-key functionality was supported and the design was very limited to a thick rectangular case Toshiba NB100 Battery .

None of the known optical technologies were ever developed to a mass production stage, with the exception of MOBBAL Keyboard Technology by Aymer International. MOBBAL Technology allows almost any shape and design of the keyboard, and can be used for laptop and desktop keyboards, ATM keypads etc Toshiba Satellite M65 battery .

The advantage of the optical keyboard technology is that it offers a real waterproof keyboard, resilient to dust and liquids, it is electromagnetic emissions free (thus cannot be eavesdropped to wirelessly) and it uses about 20% PCB volume, compare with the membrane keyboard or dome switch keyboards, significantly reducing the electronic waste Toshiba Satellite M60 battery .

The advantage of the optical keyboard technology over other keyboards such as Hall effect keyboard, laser keyboard, roll-up keyboard and transparent keyboard lies in cost (Hall effect keyboard) and feel – the optical keyboard technology do not require different key mechanism Dell Latitude D830 Battery ,

typing tactile feeling remains to offer its user the same known feeling of the keyboard, for over 60 years.

The specialist Datahand keyboard uses optical technology to sense keypresses, with a single light beam and sensor per key Dell Latitude D620 Battery .

The keys are held in their rest position by magnets; when the magnetic force is overcome to press a key, the optical path is unblocked and the keypress is registered.


When pressing a keyboard key, the key "bounces" like a ball against its contacts several times before it settles into firm contact Dell Inspiron Mini 10 Battery .

When released, it bounces some more until it reverts to the uncontacted state. If the computer was watching for each pulse, it would see many keystrokes for what the user thought was just one.

To resolve this problem, the processor in a keyboard (or computer) "debounces" the keystrokes Sony VGN-FW11S Battery ,

by aggregating them across time to produce one "confirmed" keystroke that (usually) corresponds to what is typically a solid contact. It could be argued that the dome switch technology outlined above owes its popularity to the ability of the processor to accurately debounce the keystrokes Sony VGN-FW11M Battery .

Early membrane keyboards limited typing speed because they had to do significant debouncing. This was a noticeable problem on the ZX81.


Keytops are used on full-travel keyboards Sony VGN-FW139E/H battery .

While modern keycaps are typically surface-printed, they can also be 2-shot molded, laser printed, sublimation printed, engraved, or they can be made of transparent material with printed paper inserts.

There are also Keycaps, which are thin shells that are placed over keytop bases. These were especially used on IBM PC keyboards Dell Latitude E5400 Battery .

Other parts of the PC keyboard

The modern PC keyboard also includes a control processor and indicator lights to provide feedback to the user about what state the keyboard is in Dell Latitude E4200 Battery .

Depending on the sophistication of the controller's programming, the keyboard may also offer other special features. The processor is usually a single chip 8048 microcontroller variant Dell Inspiron 300M Battery .

The keyboard switch matrix is wired to its inputs and it processes the incoming keystrokes and sends the results down a serial cable (the keyboard cord) to a receiver in the main computer box. It also controls the illumination of the "caps lock", "num lock" and "scroll lock" lights Dell Vostro A840 Battery .

A common test for whether the computer has crashed is pressing the "caps lock" key. The keyboard sends the key code to the keyboard driver running in the main computer; if the main computer is operating, it commands the light to turn on. All the other indicator lights work in a similar way Dell Studio 1737 battery .

The keyboard driver also tracks the shift, alt and control state of the keyboard.

Keyboard switch matrix

The keyboard switch matrix is often drawn with horizontal wires and vertical wires in a grid which is called a matrix circuit Dell Inspiron E1505 battery .

It has a switch at some or all intersections, much like a multiplexed display. Almost all keyboards have only the switch at each intersection, which causes "ghost keys" and "key jamming" when multiple keys are pressed (see rollover (key) ) Dell RM791 battery .

Certain, often more expensive keyboards have a diode between each intersection, allowing the keyboard microcontroller to accurately sense any number of simultaneous keys being pressed, without generating erroneous ghost keys Dell XPS M1530 battery .

A keypunch is a device for manually entering data into punched cards by precisely punching holes at locations designated by the keys struck by the operator. Early keypunches were manual devices. Later keypunches were mechanized, often resembled a small desk Dell XPS M2010 battery ,

with a keyboard similar to a typewriter, and with hoppers for blank cards and stackers for punched cards. Some keypunch models could print at the top of columns, the character punched in each of those columns. The small pieces punched out by a keypunch fell into a chad box , or (at IBM) chip box, or bit bucket Acer Aspire One battery .

In many data processing facilities the punched cards were verified by keying exactly the same data a second time and then checking to see if the second keying and the punched data were the same. There was a great demand for keypunch operators, usually women Toshiba Satellite P10 Battery ,

who worked full-time on keypunch and verifier machines, often in large keypunch departments with dozens or hundreds of other operators.

Most IBM keypunch and verifiers used a common electrical/mechanical design in their keyboards to encode the mechanical keystrokes SONY VGN-FZ210CE Battery .

As a key was depressed, a link on the keystem tripped a corresponding set of bails at the top of the keyboard assembly. The bails in turn made (closed) contacts to encode the characters electrically Dell Precision M70 Battery .

As each key stroke was detected by the machine, a feed-back circuit energized a pair of magnets with a bail which restored the keystem mechanically,reset the bails performing the electrical encoding, and gave the "feel" and sound to the operator of a completed action Toshiba Satellite L305 Battery .

Each machine had a tendency to develop a "feel" of its own based on several variables such as the amount of wear, dirt,and clearance of the bail contacts within the keyboard, as well as factors in the base machine. The keyboards however, had no provision for adjusting the "feel" other than the correct adjustment of the contacts on the restore bail contacts and the encoding bail contacts Toshiba Satellite T4900 Battery .

Special function keys such as shift, release, duplication and others, had only electrical contacts under their stems, with no mechanical linkage to the bail assembly for encoding Toshiba PA3399U-2BRS battery .

IBM keypunches such as the 024, 026 and 029 provided for the mounting of a program card that controlled various functions, such as tabbing and automatic duplication of fields from the previous card. The later 129 used electronic circuit cards to store simple programs written by the keypunch operator Toshiba Satellite A200 Battery .

Keypunches were popular through the 1970s but were rapidly made obsolete by the availability of graphical terminals

Hollerith and IBM Keypunches, 1890 through 1930s

Herman Hollerith's first device for punching cards from the 1890s was ...any ordinary ticket punch, cutting a round hole 3/16 of an inch in diameter Toshiba Satellite 1200 Battery .

Use of such a punch was facilitated by placing the holes to be used near the edges of the card. Hollerith soon developed a more accurate, simpler to use, Keyboard Punch, using a pantograph to link a punch mechanism to a guide pointer that an operator would place over the appropriate mark in a 12 by 20 matrix to line up a manual punch over correct hole in one of 20 columns Toshiba Satellite M300 Battery .

In 1901 Hollerith patented a mechanism where an operator pressed one of 12 keys to punch a hole, with the card automatically advancing to the next column. This first generation Type 001 keypunch used 45 columns and round holes Sony Vaio PCG-5G2L Battery .

In 1923 CTR (renamed IBM in 1924) introduced the first electric keypunch, the Type 011 Electric Keypunch , a similar looking device where each key closed an electrical contact that activated a solenoid which punched the hole. Later IBM keypunches included the Type 016 Motor-Driven Electric Duplicating Keypunch (1929) Sony Vaio PCG-5G3L Battery ,

the Type 31 Alphabetical Duplicating Punch (1933) ,and the Type 32 Alphabetical Printing Punch (1933). See Early Card Punch Machines at Columbia University Computing History

The IBM 024 Card Punch and IBM 026 Printing Card Punch were announced in 1949 Sony Vaio PCG-5J1L Battery .

They were almost identical, with the exception of the printing mechanism.

The heart of the 024 and 026 keypunches was a set of twelve precision punches, one per card row, each with an actuator of relatively high power Sony Vaio PCG-5K2L Battery .

Punch cards were stepped across the punch one column at a time, and the appropriate punches were activated to create the holes, resulting in a distinctive "chunk, chunk" sound as columns were punched. The 026 could print the punched character above each column Sony Vaio PCG-5J2L Battery .

There were two popular versions with slightly different character sets. The scientific version printed parentheses, equal sign and plus sign in place of four less frequently used characters in the commercial character set: percent, lozenge, pound, and ampersand. The character was printed using a 5x7 dot matrix array of wires Sony Vaio PCG-5K1L Battery ;

the device from which it derived the shape of the character was a metal plate, called the "code plate," with space for 1960 pins (35 pins times 56 printable characters). If the dot was not to be printed in a given character, the pin was machined off. By correctly positioning the plate and pressing it against one end of the array of printing wires Sony Vaio PCG-5L1L Battery ,

only the correct wires were pressed against the ribbon and then the punched card. (This printer mechanism was generally considered by IBM Customer Engineers to be difficult to repair. One of the most common problems was wires breaking in the tightly curved narrow tube between the code plate and the ribbon Sony Vaio PCG-6S2L Battery

- extracting the fragments and replacing the bundle of 35 wires was very tedious!) The printing mechanism was prone to be damaged if a user attempted to duplicate "binary" cards with non-standard punch patterns. These could cause the code-plate positioning mechanism to try to shift the plate beyond its intended range of motion, sometimes causing damage Sony Vaio PCG-6S3L Battery .

Turning off printing did not actually prevent the damage, as many people assumed, because the code-plate mechanism remained engaged with the punch unit and shifted the code plate. Turning off printing only suppressed pressing the printing pins into the ribbon and card Sony Vaio PCG-6V1L Battery .

Logic consisted of diodes, 25L6 vacuum tubes and relays. The tube circuits used 150VDC, but this voltage was only used to operate the punch-clutch magnet. Most other circuits used 48VDC Sony Vaio PCG-6W1L Battery .

Raymond Loewy, industrial designer of "streamlined" motifs who also designed railway passenger cars of the 1930s and 1940s, did the award winning external design of the 026/024 series for IBM. Their heavy steel construction and rounded corners (photos) indeed echo the industrial Art Deco style Sony Vaio PCG-6W2L Battery .

IBM 056 Card Verifier

The IBM 056 was the verifier companion to the 024 Card Punch and 026 Printing Card Punch. The verifier was similar to the 026 keypunch except for a red error lens in the machine cover lower center Sony Vaio PCG-6W3L Battery .

The verifier operator entered exactly the same data as the keypunch operator and the verifier machine thenchecked to see if the punched data matched. Successfully verified cards had a small notch punched on the right hand edge Sony Vaio PCG-7111L Battery .

The IBM 056 verifier used most of the same mechanical and electrical components as the 024/026 keypunch machines with the exception of the punch unit and print head. The punch unit had sensing pins in place of the punches. The holes sensed or not sensed would trip a contact bail when the configuration was other than that entered by the verifier operator Sony Vaio PCG-7112L Battery .

This stopped the forward motion of the card, and presented a red error light on the machine cover. The notching mechanism was located in the area occupied by the print mechanism on a 026 printing keypunch. It had a solenoid which drove the notching mechanism, and another that selected the top notch punch or end of card punch Sony Vaio PCG-7113L Battery .

When an operator keying data to be verified encountered an error the operator was given a second and third try to re-enter the data that was supposed to be in the field. If the third try was incorrect an error notch was put on the top of the card over the column with the error and the "OK" punch at the end of the card was not enabled Sony Vaio PCG-7133L Battery .

The data in the card could actually be correct upon occasion as the verifier operator was capable of making errors as well as the keypunch operator. However with three tries, the operator was less likely to repeatedly make the same error Sony Vaio PCG-7Z2L Battery .

Some verifier operators were able to guess the error on the card created by the previous keypunch operator, defeating the purpose of the verify procedure, and thus some machines were altered to allow only one entry and error notched on the second try Sony Vaio PCG-8Y1L Battery .

Cards with error notches were re-punched (using an 024 or 026) usually by "duplicating" to the column in error, then entering the correct data. The "duplicating function was accomplished by feeding the card through the punch station without punching it Sony Vaio PCG-8Y2L Battery .

At the next station sensing pins read the holes present in the original card and transferred the data to the punching station and into a blank card. Columns with errors were corrected instead of being duplicated. The corrected card was then verified to check the data again and be "OK notched" Sony Vaio PCG-8Z1L Battery .

IBM 824 and 826 Typewriter Card Punches

The IBM 824 Typewriter Card Punch was an IBM 024 where the 024 keyboard was replaced by an IBM electric typewriter, permitting selected text to be typed and punched. The IBM 826 used an IBM 026 Keypunch Sony Vaio PCG-8Z2L Battery .

IBM 029

Introduced with System/360 in 1964, the 029 had new character codes for parentheses, equal and plus as well as other new symbols used in the EBCDIC code Sony VAIO PCG-5G2L Battery .

The IBM 029 was mechanically similar to the IBM 026 and printed the punched character on the top of the card using the same kind of mechanism as the 026, although it used a larger code plate with 2240 printing-pin sites due to the larger set of characters in EBCDIC Sony VAIO PCG-5G3L Battery .

The 029's logic consisted of wire contact relays on later models and reed relays and diodes on SMS cards for early ones. The more "advanced" reed relays used at first proved to be less reliable than expected, causing IBM to revert to the older-style wire-contact relay-based design Sony VAIO PCG-5J1L Battery .

All ran on 48 volts direct current, and did not require vacuum tubes, as were used in the 024/026. A common additional feature made available (at additional cost) was the leading zeros feature (termed "Left-Zero"). This was delivered by an additional set of four SMS cards Sony VAIO PCG-5K2L Battery .

The field was programmed for leading zeros using the program card. If it was (say) a six digit field, the operator only had to key in the actual value (for example 73). The feature would then fill the field by punching the leading four zeros, followed by the 73, in effect right justifying the field, thus: 000073 Sony VAIO PCG-5J2L Battery .

IBM 059 Card Verifier

The IBM 059 was the Verifier companion to the IBM 029 Card Punch. In design, it differed radically from the earlier 056 verifier, in that it used optical sensing of card holes instead of mechanical sensing pins Sony VAIO PCG-5K1L Battery .

This made the 059 much quieter than the 056 (which was often actually louder than the 024 keypunch!). The optical sensors used a single light source, which was distributed to various sites within the machine via fiber-optic lightpipes. Despite the technology, the basic mode of operation remained essentially the same as with the 056 Sony VAIO PCG-5L1L Battery .

Ironically, not all verifier operators appreciated the noise reduction. When used in a room also containing 029 keypunch machines, the verifier operators sometimes missed the auditory feedback provided by the loud "thunk" noise emitted by the older 059. Some were known to compensate by hitting the keys harder, sometimes actually wearing out keyboard parts Sony VAIO PCG-6S2L Battery.

IBM 129 Card Data Recorder

Introduced with the System/370 in 1971, the IBM 129 was capable of both punching and verifying. A switch on the keyboard unit provided the ability to toggle between the two modes Sony VAIO PCG-6S3L Battery .

The transistorized IBM 129 Card Data Recorder's primary advantage over the 029 was that it featured an electronic 80-column buffer to hold the card image. When using earlier keypunches, a keystroke error required the card to be ejected by pressing the Release and Register keys Sony VAIO PCG-6V1L Battery ,

the error corrected by pressing the Duplicate key until the wrong column was reached, typing the correct data for the rest of that card, then pressing the Release key and manually removing the bad card from the output card stacker before it was placed in the deck (this required some practice, but quickly became an automatic action that you no longer had to think about) Sony VAIO PCG-6W1L Battery .

With the 129 a keystroke error could be erased by pressing the Backspace key and re-keyed. The entire 80-column card was punched automatically, as fast as the mechanism could go, when the Release key was pressed Sony VAIO PCG-6W2L Battery .

Logic was in SLT modules.

A secondary advantage of the 129 was that the speed of the keying operation was not limited by punching each column at the time of the keystroke Sony VAIO PCG-6W3L Battery .

The 129 could store six programs in its memory, selectable by a rotary switch. Unlike earlier keypunch machines, the program cards were read into memory via the regular card-feed path, and were not wrapped around a "program drum" Sony VAIO PCG-7111L Battery .

Thanks to its use of electronic memory, the 129 did not have a separate "read station" with a pin-sense unit to enable duplication of data from one card to the next. Instead, duplication was based on the stored image of the previous card. Cards could also be "read-in" through an optical read unit integrated into the punch station Sony VAIO PCG-7112L Battery .

Program card

Program card for an IBM 026 at the Computer History Museum. The lever at the top opened the metal clamp holding the card in place Sony VAIO PCG-7113L Battery .

The column-80 edge of the card was inserted under the clamp first. Small fingers on the right side of the clamp helped guide the column-1 edge into position. The lever was then rotated back to secure the card.

IBM 024, 026, and 029 keypunches and their companion verifiers, the 056 and 059, could be programmed to a limited extent using a Program Card Sony VAIO PCG-7133L Battery .

The keypunch or verifier could be programmed to automatically advance to the beginning of each field, default to certain character types within the field, duplicate a field from the previous card, and so on. Program cards were an improvement over the Skip Bar used in some earlier keypunches Sony VAIO PCG-7Z1L Battery .

The program was encoded on a punched card and could be prepared on any keypunch (a keypunch would operate even if no program card was in place). The program card was wrapped around the program drum, and clamped in place. The drum rotated as the card being punched moved through the punching mechanism Sony VAIO PCG-7Z2L Battery .

The holes in the program card were sensed by an array of starwheels that would cause levers to rise and fall as the holes in the program card passed beneath the starwheels, activating electrical contacts. The program was encoded in the top six rows Sony VAIO PCG-8Y1L Battery .

If the optional Second Programfeature was installed, another program could be encoded in the bottom six rows . A switch let the operator select which program to use. The central cover on the keypunch could be tilted open toward the operator and a locking lever released, allowing the program drum to be removed and replaced Sony VAIO PCG-8Y2L Battery .

The program card was punched with characters that controlled its function as follows:

Many programming languages, such as FORTRAN, the RPG programming language or the IBM Assembler, coded operations in specific card columns, such as 1, 10, 16, 36, and 72 Sony VAIO PCG-8Z1L Battery .

The program card for such a setup might be coded as:

In this example, if the keypunch operator typed a few characters at the beginning of the card and then pressed the skip key, the keypunch would tab to column 10 Sony VAIO PCG-8Z2L Battery .

Note: "Field Definition" (12) and "Alphabetic Shift" (1) prints as an A. If program 2 codes were punched, invalid characters could be generated that the printer did not know how to print, some of which could even damage the printer Sony VGP-BPS21 Battery !

Program cards could automate certain tasks, such as "gang punching", the insertion of a constant field into each card of a deck of cards. For amusement, program cards could even be set up to play music by gang-punching "noisy" characters (characters represented by many holes, usually special characters) and "quiet" numbers and letters in rhythmic patterns Sony VGP-BPS21A Battery .

IBM Keypunch for 96 column cards

IBM, in the early 1970s, introduced the System/3 family of low-end business computers which featured a new, smaller sized, punch card format with 96 columns Sony VGP-BPS21B Battery .

IBM 5496 Data Recorder, a keypunch machine with print and verify functions, and IBM 5486 Card Sorter were made for these 96-column cards .

Powers, Remington Rand (UNIVAC) Keypunches

Beginning in about 1906 an employee of the Census Bureau, James Powers, developed the Powers Keypunch specific to the census application, with 240 keys Sony VGP-BPS21/S Battery .

In 1911 Powers formed Powers Accounting Machine Company, later merged with others to form Remington Rand. Remington Rand's UNIVAC division made keypunches for their 90-column cards and similar machines for the IBM 80-column card Sony VGP-BPS21A/B Battery .

Their 90-column keypunches used a mechanical system developed by Remington Rand to avoid IBM patent issues (long before the acquisition of Eckert-Mauchly Computer Corporation), that stored the entire card image and punched all holes on the entire card simultaneously SONY VGP-BPS21 Battery .

Remington Rand keypunches included: UNIVAC Card Code Punch Type 306-5, 90 Column Alphabetical (Types 306-2, 306-3), 90 Column Numerical (Types 204-2, 204-3), Portable Electric Punch Type 202, Spot Punch Type 301, and the Automatic Verifying Machine Type 313 SONY VGP-BPS21A Battery .

The Type 306-2 provided for verification; the cards were passed through the keypunch a second time and keyed again. The verify-punching of the same cards in the same sequence ... results in the elongation of perforations for correct information SONY VGP-BPS21B Battery .

Round perforations indicate incorrect information. Complete and rapid detection of errors is performed mechanically by the Automatic Verifying Machine SONY VGP-BPS21/S Battery SONY VGP-BPS21A/B Battery .

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