Main article: Keyboard technology
Key switches[edit]
This breadth possibly contains aboriginal research. Please advance it by acceptance the claims fabricated and abacus inline citations. Statements consisting alone of aboriginal analysis should be removed. (August 2013)
In the aboriginal cyberbanking keyboards in the aboriginal 1970s, the key switches were alone switches amid into holes in metal frames. These keyboards amount from 80–120 US dollars and were acclimated in mainframe abstracts terminals. The a lot of accustomed about-face types were reed switches (contacts amid in a exhaustion in a bottle capsule, afflicted by a allurement army on the about-face plunger).[citation needed]
In the mid-1970s, lower-cost direct-contact key switches were introduced, but their activity in about-face cycles was abundant beneath (rated ten actor cycles) because they were accessible to the environment. This became added acceptable, however, for use in computer terminals at the time, which began to see added beneath archetypal lifespans as they advanced.
In 1978, Key Tronic Corporation alien keyboards with capacitive-based switches, one of the aboriginal keyboard technologies to not use absolute switches. There was artlessly a blot pad with a conductive-coated Mylar bogus breadth on the about-face plunger, and two arch trace patterns on the printed ambit lath below. As the key was depressed, the capacitance amid the plunger pad and the patterns on the PCB beneath changed, which was detected by chip circuits (IC). These keyboards were claimed to accept the aforementioned believability as the added "solid-state switch" keyboards such as anterior and Hall-Effect, but aggressive with direct-contact keyboards. Prices of $60 for keyboards were accomplished and Key Tronic rapidly became the better absolute keyboard manufacturer.
Meanwhile, IBM fabricated their own keyboards, appliance their own patented technology: Keys on earlier IBM keyboards were fabricated with a "buckling spring" mechanism, in which a braid animation beneath the key buckles beneath burden from the user's finger, triggering a bang that presses two bogus bedding (membranes) with conductive traces together, commutual a circuit. This produces a beat sound, and gives concrete acknowledgment for the typist advertence that the key has been depressed.[12]
The aboriginal cyberbanking keyboards had a typewriter key biking ambit of 0.187 inches (4.75 mm), keytops were a half-inch (12.7 mm) high, and keyboards were about two inches (5 cm) thick. Over time, beneath key biking was accustomed in the MARKET
, assuredly landing on 0.110 inches (2.79 mm). Coincident with this, Key Tronic was the aboriginal aggregation to acquaint a keyboard which was alone about one inch thick. And now keyboards admeasurement alone about a half-inch thick.
Keytops are an important aspect of keyboards. In the beginning, keyboard keytops had a "dish shape" on top, like typewriters afore them. Keyboard key legends accept to be acutely abiding over tens of millions of depressions, back they are subjected to acute automated abrasion from fingers and fingernails, and accountable to duke OILS and creams, so block and bushing key legends with paint, as was done ahead for alone switches, was never acceptable. So, for the aboriginal cyberbanking keyboards, the key legends were produced by two-shot (or double-shot, or two-color) molding, breadth either the key carapace or the central of the key with the key fable was molded first, and again the added blush molded second. But, to save cost, added methods were explored, such as sublimation press and laser engraving, both methods which could be acclimated to book a accomplished keyboard at the aforementioned time.
Initially, sublimation printing, breadth a appropriate ink is printed assimilate the keycap apparent and the appliance of calefaction causes the ink molecules to access and amalgamate with the bogus modules, had a botheration because feel oils acquired the molecules to disperse, but again a necessarily actual harder bright blanket was activated to anticipate this. Coincident with sublimation printing, which was aboriginal acclimated in top aggregate by IBM on their keyboards, was the addition by IBM of single-curved-dish keycaps to facilitate superior press of key legends by accepting a consistently arced apparent instead of a dish. But one botheration with sublimation or laser press was that the processes took too continued and alone aphotic legends could be printed on light-colored keys. On addition note, IBM was altered in appliance abstracted shells, or "keycaps", on keytop bases. This ability accept fabricated their accomplishment of altered keyboard layouts added flexible, but the acumen for accomplishing this was that the bogus actual that bare to be acclimated for sublimation press was altered from accepted ABS keytop bogus material.
Three final automated technologies brought keyboards to breadth they are today, active the amount able-bodied beneath $10:
"Monoblock" keyboard designs were developed breadth alone about-face housings were alone and a jumpsuit "monoblock" apartment acclimated instead. This was accessible because of abstraction techniques that could accommodate actual bound tolerances for the switch-plunger holes and guides beyond the amplitude of the keyboard so that the key plunger-to-housing clearances were not too bound or too loose, either of which could could cause the keys to bind.
The use of contact-switch film bedding beneath the monoblock. This technology came from flat-panel about-face membranes, breadth the about-face contacts are printed central of a top and basal layer, with a spacer band in between, so that if burden is activated to the breadth above, a absolute electrical acquaintance is made. The film layers can be printed by very-high volume, bargain "reel-to-reel" press machines, with anniversary keyboard film cut and punched out afterwards.
Plastic abstracts played a actual important allotment in the development and advance of cyberbanking keyboards. Until "monoblocks" came along, GE's "self-lubricating" Delrin was the alone bogus actual for keyboard about-face plungers that could bear the assault over tens of millions of cycles of lifetime use. Greasing or OILING about-face plungers was abominable because it would allure clay over time which would eventually affect the feel and even bind the key switches (although keyboard manufacturers would sometimes bastard this into their keyboards, abnormally if they could not ascendancy the tolerances of the key plungers and housings able-bodied abundant to accept a bland key abasement feel or anticipate binding). But Delrin was alone accessible in atramentous and white, and was not acceptable for keytops (too soft), so keytops use ABS plastic. However, as bogus abstraction avant-garde in advancement bound tolerances, and as key biking breadth bargain from 0.187-inch to 0.110-inch (4.75 mm to 2.79 mm), single-part keytop/plungers could be fabricated of ABS, with the keyboard monolocks aswell fabricated of ABS.
Control processor[edit]
Scanning procedure
Computer keyboards cover ascendancy chip to catechumen key presses into key codes (usually scancodes) that the computer's electronics can understand. The key switches are affiliated via the printed ambit lath in an electrical X-Y cast breadth a voltage is provided sequentially to the Y curve and, if a key is depressed, detected sequentially by scanning the X lines.
The aboriginal computer keyboards were for mainframe computer abstracts terminals and acclimated alone cyberbanking parts. The aboriginal keyboard chip was alien in 1972 by General Instruments, but keyboards accept been appliance the single-chip 8048 microcontroller alternative back it became accessible in 1978. The keyboard about-face cast is active to its inputs, it converts the keystrokes to key codes, and, for a alone keyboard, sends the codes down a consecutive cable (the keyboard cord) to the capital processor on the computer motherboard. This consecutive keyboard cable advice is alone bi-directional to the admeasurement that the computer's electronics controls the beam of the caps lock, num lock and annal lock lights.
One analysis for whether the computer has comatose is acute the caps lock key. The keyboard sends the key cipher to the keyboard disciplinarian active in the capital computer; if the capital computer is operating, it commands the ablaze to about-face on. All the added indicator lights plan in a agnate way. The keyboard disciplinarian aswell advance the Shift, alt and ascendancy accompaniment of the keyboard.
Some lower-quality keyboards accept assorted or apocryphal key entries due to bare electrical designs. These are acquired by bare keyswitch "debouncing" or bare keyswitch cast blueprint that don't acquiesce assorted keys to be depressed at the aforementioned time, both affairs which are explained below:
When acute a keyboard key, the key contacts may "bounce" adjoin anniversary added for several milliseconds afore they achieve into close contact. If released, they animation some added until they backslide to the uncontacted state. If the computer were watching for anniversary pulse, it would see abounding keystrokes for what the user anticipation was just one. To boldness this problem, the processor in a keyboard (or computer) "debounces" the keystrokes, by accumulation them beyond time to aftermath one "confirmed" keystroke.
Some low-quality keyboards aswell ache problems with rollover (that is, if assorted keys apprenticed at the aforementioned time, or if keys are apprenticed so fast that assorted keys are down aural the aforementioned milliseconds). Aboriginal "solid-state" keyswitch keyboards did not accept this botheration because the keyswitches are electrically abandoned from anniversary other, and aboriginal "direct-contact" keyswitch keyboards abhorred this botheration by accepting abreast diodes for every keyswitch. These aboriginal keyboards had "n-key" rollover, which agency any amount of keys can be depressed and the keyboard will still admit the next key depressed. But if three keys are apprenticed (electrically closed) at the aforementioned time in a "direct contact" keyswitch cast that doesn't accept abreast diodes, the keyboard electronics can see a fourth "phantom" key which is the circle of the X and Y curve of the three keys. Some types of keyboard chip will annals a best amount of keys at one time. "Three-key" rollover, aswell alleged "phantom key blocking" or "phantom key lockout", will alone annals three keys and avoid all others until one of the three keys is lifted. This is undesirable, abnormally for fast accounting (hitting new keys afore the fingers can absolution antecedent keys), and amateur (designed for assorted key presses).
As direct-contact film keyboards became popular, the accessible rollover of keys was optimized by allegory the a lot of accepted key sequences and agreement these keys so that they do not potentially aftermath apparition keys in the electrical key cast (for example, artlessly agreement three or four keys that ability be depressed accompanying on the aforementioned X or aforementioned Y line, so that a apparition key intersection/short cannot happen), so that blocking a third key usually isn't a problem. But lower-quality keyboard designs and apprenticed engineers may not apperceive these tricks, and it can still be a botheration in amateur due to berserk altered or configurable layouts in altered games.
Connection types[edit]
There are several means of abutting a keyboard to a arrangement assemblage (more precisely, to its keyboard controller) appliance cables, including the accepted AT adapter frequently begin on motherboards, which was eventually replaced by the PS/2 and the USB connection. Prior to the iMac band of systems, Apple acclimated the proprietary Apple Desktop Bus for its keyboard connector.
Wireless keyboards accept become accustomed for their added user freedom. A wireless keyboard generally includes a appropriate aggregate transmitter and receiver assemblage that attaches to the computer's keyboard port. The wireless aspect is accomplished either by radio abundance (RF) or by bittersweet (IR) signals beatific and accustomed from both the keyboard and the assemblage absorbed to the computer. A wireless keyboard may use an industry accepted RF, alleged Bluetooth. With Bluetooth, the transceiver may be congenital into the computer. However, a wireless keyboard needs batteries to plan and may affectation a aegis botheration due to the accident of abstracts "eavesdropping" by hackers. Wireless solar keyboards allegation their batteries from baby solar panels appliance sunlight or accepted bogus lighting. An aboriginal archetype of a customer wireless keyboard is that of the Olivetti Envision.
Key switches[edit]
This breadth possibly contains aboriginal research. Please advance it by acceptance the claims fabricated and abacus inline citations. Statements consisting alone of aboriginal analysis should be removed. (August 2013)
In the aboriginal cyberbanking keyboards in the aboriginal 1970s, the key switches were alone switches amid into holes in metal frames. These keyboards amount from 80–120 US dollars and were acclimated in mainframe abstracts terminals. The a lot of accustomed about-face types were reed switches (contacts amid in a exhaustion in a bottle capsule, afflicted by a allurement army on the about-face plunger).[citation needed]
In the mid-1970s, lower-cost direct-contact key switches were introduced, but their activity in about-face cycles was abundant beneath (rated ten actor cycles) because they were accessible to the environment. This became added acceptable, however, for use in computer terminals at the time, which began to see added beneath archetypal lifespans as they advanced.
In 1978, Key Tronic Corporation alien keyboards with capacitive-based switches, one of the aboriginal keyboard technologies to not use absolute switches. There was artlessly a blot pad with a conductive-coated Mylar bogus breadth on the about-face plunger, and two arch trace patterns on the printed ambit lath below. As the key was depressed, the capacitance amid the plunger pad and the patterns on the PCB beneath changed, which was detected by chip circuits (IC). These keyboards were claimed to accept the aforementioned believability as the added "solid-state switch" keyboards such as anterior and Hall-Effect, but aggressive with direct-contact keyboards. Prices of $60 for keyboards were accomplished and Key Tronic rapidly became the better absolute keyboard manufacturer.
Meanwhile, IBM fabricated their own keyboards, appliance their own patented technology: Keys on earlier IBM keyboards were fabricated with a "buckling spring" mechanism, in which a braid animation beneath the key buckles beneath burden from the user's finger, triggering a bang that presses two bogus bedding (membranes) with conductive traces together, commutual a circuit. This produces a beat sound, and gives concrete acknowledgment for the typist advertence that the key has been depressed.[12]
The aboriginal cyberbanking keyboards had a typewriter key biking ambit of 0.187 inches (4.75 mm), keytops were a half-inch (12.7 mm) high, and keyboards were about two inches (5 cm) thick. Over time, beneath key biking was accustomed in the MARKET
, assuredly landing on 0.110 inches (2.79 mm). Coincident with this, Key Tronic was the aboriginal aggregation to acquaint a keyboard which was alone about one inch thick. And now keyboards admeasurement alone about a half-inch thick.Keytops are an important aspect of keyboards. In the beginning, keyboard keytops had a "dish shape" on top, like typewriters afore them. Keyboard key legends accept to be acutely abiding over tens of millions of depressions, back they are subjected to acute automated abrasion from fingers and fingernails, and accountable to duke OILS
and creams, so block and bushing key legends with paint, as was done ahead for alone switches, was never acceptable. So, for the aboriginal cyberbanking keyboards, the key legends were produced by two-shot (or double-shot, or two-color) molding, breadth either the key carapace or the central of the key with the key fable was molded first, and again the added blush molded second. But, to save cost, added methods were explored, such as sublimation press and laser engraving, both methods which could be acclimated to book a accomplished keyboard at the aforementioned time.Initially, sublimation printing, breadth a appropriate ink is printed assimilate the keycap apparent and the appliance of calefaction causes the ink molecules to access and amalgamate with the bogus modules, had a botheration because feel oils acquired the molecules to disperse, but again a necessarily actual harder bright blanket was activated to anticipate this. Coincident with sublimation printing, which was aboriginal acclimated in top aggregate by IBM on their keyboards, was the addition by IBM of single-curved-dish keycaps to facilitate superior press of key legends by accepting a consistently arced apparent instead of a dish. But one botheration with sublimation or laser press was that the processes took too continued and alone aphotic legends could be printed on light-colored keys. On addition note, IBM was altered in appliance abstracted shells, or "keycaps", on keytop bases. This ability accept fabricated their accomplishment of altered keyboard layouts added flexible, but the acumen for accomplishing this was that the bogus actual that bare to be acclimated for sublimation press was altered from accepted ABS keytop bogus material.
Three final automated technologies brought keyboards to breadth they are today, active the amount able-bodied beneath $10:
"Monoblock" keyboard designs were developed breadth alone about-face housings were alone and a jumpsuit "monoblock" apartment acclimated instead. This was accessible because of abstraction techniques that could accommodate actual bound tolerances for the switch-plunger holes and guides beyond the amplitude of the keyboard so that the key plunger-to-housing clearances were not too bound or too loose, either of which could could cause the keys to bind.
The use of contact-switch film bedding beneath the monoblock. This technology came from flat-panel about-face membranes, breadth the about-face contacts are printed central of a top and basal layer, with a spacer band in between, so that if burden is activated to the breadth above, a absolute electrical acquaintance is made. The film layers can be printed by very-high volume, bargain "reel-to-reel" press machines, with anniversary keyboard film cut and punched out afterwards.
Plastic abstracts played a actual important allotment in the development and advance of cyberbanking keyboards. Until "monoblocks" came along, GE's "self-lubricating" Delrin was the alone bogus actual for keyboard about-face plungers that could bear the assault over tens of millions of cycles of lifetime use. Greasing or OILING
about-face plungers was abominable because it would allure clay over time which would eventually affect the feel and even bind the key switches (although keyboard manufacturers would sometimes bastard this into their keyboards, abnormally if they could not ascendancy the tolerances of the key plungers and housings able-bodied abundant to accept a bland key abasement feel or anticipate binding). But Delrin was alone accessible in atramentous and white, and was not acceptable for keytops (too soft), so keytops use ABS plastic. However, as bogus abstraction avant-garde in advancement bound tolerances, and as key biking breadth bargain from 0.187-inch to 0.110-inch (4.75 mm to 2.79 mm), single-part keytop/plungers could be fabricated of ABS, with the keyboard monolocks aswell fabricated of ABS.Control processor[edit]
Scanning procedure
Computer keyboards cover ascendancy chip to catechumen key presses into key codes (usually scancodes) that the computer's electronics can understand. The key switches are affiliated via the printed ambit lath in an electrical X-Y cast breadth a voltage is provided sequentially to the Y curve and, if a key is depressed, detected sequentially by scanning the X lines.
The aboriginal computer keyboards were for mainframe computer abstracts terminals and acclimated alone cyberbanking parts. The aboriginal keyboard chip was alien in 1972 by General Instruments, but keyboards accept been appliance the single-chip 8048 microcontroller alternative back it became accessible in 1978. The keyboard about-face cast is active to its inputs, it converts the keystrokes to key codes, and, for a alone keyboard, sends the codes down a consecutive cable (the keyboard cord) to the capital processor on the computer motherboard. This consecutive keyboard cable advice is alone bi-directional to the admeasurement that the computer's electronics controls the beam of the caps lock, num lock and annal lock lights.
One analysis for whether the computer has comatose is acute the caps lock key. The keyboard sends the key cipher to the keyboard disciplinarian active in the capital computer; if the capital computer is operating, it commands the ablaze to about-face on. All the added indicator lights plan in a agnate way. The keyboard disciplinarian aswell advance the Shift, alt and ascendancy accompaniment of the keyboard.
Some lower-quality keyboards accept assorted or apocryphal key entries due to bare electrical designs. These are acquired by bare keyswitch "debouncing" or bare keyswitch cast blueprint that don't acquiesce assorted keys to be depressed at the aforementioned time, both affairs which are explained below:
When acute a keyboard key, the key contacts may "bounce" adjoin anniversary added for several milliseconds afore they achieve into close contact. If released, they animation some added until they backslide to the uncontacted state. If the computer were watching for anniversary pulse, it would see abounding keystrokes for what the user anticipation was just one. To boldness this problem, the processor in a keyboard (or computer) "debounces" the keystrokes, by accumulation them beyond time to aftermath one "confirmed" keystroke.
Some low-quality keyboards aswell ache problems with rollover (that is, if assorted keys apprenticed at the aforementioned time, or if keys are apprenticed so fast that assorted keys are down aural the aforementioned milliseconds). Aboriginal "solid-state" keyswitch keyboards did not accept this botheration because the keyswitches are electrically abandoned from anniversary other, and aboriginal "direct-contact" keyswitch keyboards abhorred this botheration by accepting abreast diodes for every keyswitch. These aboriginal keyboards had "n-key" rollover, which agency any amount of keys can be depressed and the keyboard will still admit the next key depressed. But if three keys are apprenticed (electrically closed) at the aforementioned time in a "direct contact" keyswitch cast that doesn't accept abreast diodes, the keyboard electronics can see a fourth "phantom" key which is the circle of the X and Y curve of the three keys. Some types of keyboard chip will annals a best amount of keys at one time. "Three-key" rollover, aswell alleged "phantom key blocking" or "phantom key lockout", will alone annals three keys and avoid all others until one of the three keys is lifted. This is undesirable, abnormally for fast accounting (hitting new keys afore the fingers can absolution antecedent keys), and amateur (designed for assorted key presses).
As direct-contact film keyboards became popular, the accessible rollover of keys was optimized by allegory the a lot of accepted key sequences and agreement these keys so that they do not potentially aftermath apparition keys in the electrical key cast (for example, artlessly agreement three or four keys that ability be depressed accompanying on the aforementioned X or aforementioned Y line, so that a apparition key intersection/short cannot happen), so that blocking a third key usually isn't a problem. But lower-quality keyboard designs and apprenticed engineers may not apperceive these tricks, and it can still be a botheration in amateur due to berserk altered or configurable layouts in altered games.
Connection types[edit]
There are several means of abutting a keyboard to a arrangement assemblage (more precisely, to its keyboard controller) appliance cables, including the accepted AT adapter frequently begin on motherboards, which was eventually replaced by the PS/2 and the USB connection. Prior to the iMac band of systems, Apple acclimated the proprietary Apple Desktop Bus for its keyboard connector.
Wireless keyboards accept become accustomed for their added user freedom. A wireless keyboard generally includes a appropriate aggregate transmitter and receiver assemblage that attaches to the computer's keyboard port. The wireless aspect is accomplished either by radio abundance (RF) or by bittersweet (IR) signals beatific and accustomed from both the keyboard and the assemblage absorbed to the computer. A wireless keyboard may use an industry accepted RF, alleged Bluetooth. With Bluetooth, the transceiver may be congenital into the computer. However, a wireless keyboard needs batteries to plan and may affectation a aegis botheration due to the accident of abstracts "eavesdropping" by hackers. Wireless solar keyboards allegation their batteries from baby solar panels appliance sunlight or accepted bogus lighting. An aboriginal archetype of a customer wireless keyboard is that of the Olivetti Envision.
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