A keyset or chorded keyboard (also called a chord keyboard or chording keyboard) is a computer input device that allows the user to enter characters or commands formed by pressing several keys together, like playing a "chord" on a piano. The large number of combinations available from a small number of keys allows text or commands to be entered with one hand, leaving the other hand free to do something else. A secondary advantage is that it can be built into a device (such as a pocket-sized computer) that is too small to contain a normal sized keyboard.
A chorded keyboard minus the board, typically designed to be used while held in the hand, is called a keyer.
There are many different designs based on similar concepts, some requiring only one hand for operation.
Due to the small number of keys required, chording is easily adapted from table-supported boards to hand-supported devices. In this case it may be referred to as a keyer rather than a keyboard because the keys are no longer mounted to a board. A keyer is a good replacement for a chorded keyboard in portable applications such as the wearable computer. The failure of touch typing to prevail among users throughout the world after a century of availability leads some to question the public's ability to remember the necessary chords. Others maintain that without the reward of mobility, as supplied by wearable computers, there has been little motivation.
Some claim that because the fingers do not need to move as far, chording saves time and can be faster than a regular keyboard. Others claim it is slower because a regular keyboard allows the next key to be pressed while the last key is still held down, whilst some (but not all) chording keyboards require each chord to be completely released before the next is pressed. Due to key bounce and chord overlap, deciding which chord sequence the user intends is a non-trivial matter. Definitive numbers (in words per minute) are hard to find. This is due in part to the many different designs available and multiple measurement protocols. Nevertheless, Thad Starner and his team of the Georgia Institute of Technology have started to publish scientific testing and results
Currently stenotype machines hold the record for fastest text entry. Many stenotype users can reach 300 words per minute, which as of 2007 is faster than any other text entry device (including other chorded keyboards, keyers, non-chorded keyboards, and voice recognition systems).
The first widespread use of a chord keyboard was in the stenotype machine used by court reporters, which was invented in 1868 and is still in use. But the output of the stenotype is a phonetic code that has to be transcribed later (usually by the same operator who produced the original output), rather than arbitrary text.
In 1874, the five-bit Baudot telegraph code and a matching 5-key chord keyboard was designed to be used with the operator forming the codes manually. The code is optimized for speed and low wear: chords were chosen so that the most common characters used the simplest chords. But telegraph operators were already using typewriters with QWERTY keyboards to "copy" received messages, and at the time it made more sense to build a typewriter that could generate the codes automatically, rather than making them learn to use a new input device.
Braille (a writing system for the blind) uses either 6 or 8 tactile 'points' from which all letters and numbers are formed. When Louis Braille invented it, it was produced with a needle holing successively all needed points in a cardboard sheet. In 1892, Frank Hall created the Hall braille writer which was like a typewriter with 6 keys, one for each dot in a braille cell. The Perkins Brailler, first manufactured in 1951, uses a 6-key chord keyboard (plus a spacebar) to produce braille output, and was very successful as a mass market affordable product.
After World War II, with the arrival of electronics for reading chords and looking in tables of "codes", the postal sorting offices started to research chordic solutions to be able to employ people other than trained and expensive typists. In 1954, an important concept was discovered: chordic production is easier to master when the production is done at the release of the keys instead of when they are pressed.
Researchers at IBM investigated chord keyboards for both typewriters and computer data entry as early as 1959, with the idea that it might be faster than touch-typing if some chords were used to enter whole words or parts of words. One of their designs had 14 keys that were dimpled on the edges as well as the top, so one finger could press two adjacent keys for additional combinations. Their results were inconclusive, but research continued until at least 1978.
Douglas Engelbart, in the 1968 demo made famous for the introduction of the computer mouse, operates a chording keyboard ("keyset") with one hand and a mouse or light pen with the other. His 5-key "keyset" was very similar to the one used in the original Baudot system. It generated a chorded key using a combination of the five keys held down when one of the three mouse buttons was pressed. This was able to produce 93 different chords (25-1 =32-1 multiplied by 3 mouse buttons). Photographs of the terminals used at his lab show that some users had the mouse on the left and the keyset on the right, while other users arranged them the other way around. A few users became very proficient with the mouse and keyset, but when development of the mouse moved to Xerox PARC, the keyset was left behind. Engelbart proved that trained typists, after just a few hours of training, could perform more efficiently using a chord keyboard than a conventional QWERTY keyboard.
In the early 1980s, Philips Research labs at Redhill, Surrey did a brief study into small, cheap keyboards for entering text on a telephone. One solution made use of a grid of hexagonal keys with symbols inscribed into dimples in the keys that were either in the center of a key, across the boundary of two keys, or at the joining of three keys. Pressing down on one of the dimples would cause either one, two or three of the hexagonal buttons to be depressed at the same time, forming a chord that would be unique to that symbol. With this arrangement, a nine button keyboard with three rows of three hexagonal buttons could be fitted onto a telephone and could produce up to 33 different symbols. By choosing widely separated keys, one could employ one dimple as a 'shift' key to allow both letters and numbers to be produced. With eleven keys in a 3/4/4 arrangement, 43 symbols could be arranged allowing for lowercase text, numbers and a modest number of punctuation symbols to be represented along with a 'shift' function for accessing uppercase letters. Whilst this had the advantage of being usable by untrained users via 'hunt and peck' typing and requiring one less key switch than a conventional 12 button keypad, it had the disadvantage that some symbols required three times as much force to depress them as others which made it hard to achieve any speed with the device. That solution is still alive and proposed by Fastap and Unitap among others, and a commercial phone has been produced and promoted in Canada during 2006.
The only proposed modern standard, GKOS (or Global Keyboard Optimised for Small Wireless Devices) has had little or no commercial or non-commercial development.
A userspace driver for Linux using uinput and joystick devices is usable, and having features added at: http://joy2chord.sourceforge.net/
Another early commercial models was the six-button Microwriter, designed by Cy Endfield and Chris Rainey, and first sold in 1980. Microwriting is the system of chord keying and is based on a set of mnemonics. It was designed only for right-handed use. Chris Rainey, the co-inventor of Microwriting, re-introduced Microwriting for PC and Palm PDAs with a standalone miniature chording keyboard called CyKey which caters to both left and right-handed users. CyKey (pronounced sai-ki or "psyche") is named after the Microwriter chord system's co-inventor Cy Endfield, who died in 1995 but the name also reflects its intuitive nature.
The BAT from Infogrip has been continuously sold since 1985. It provides one key for each finger and three for the thumb. It is proposed for the hand which does not hold the mouse, in an exact continuation of Engelbart vision.
A minimal chordic keyboard is the half qwerty where, to produce the letters of the missing half you just press simultaneously the space bar. It has been academically proven by Mathias and alii that people who can touch type can quickly recover 50 to 70% of their two hands operation. The loss is a solid contribution to the speed discussion above. It is implemented on two well sold mobile phones, but provided with software disambiguation, which allows to not use the space bar.
"Multiambic" keyers for use with wearable computers were invented in Canada in the 1970s. Multiambic keyers are like chording keyboards but without the board, i.e. the keys are grouped in a cluster for being handheld rather than for sitting on a flat surface.
Chording keyboards are also used as portable but two handed input devices for the visually impaired (either combined with a refreshable braille display or vocal synthesis). Such keyboards use a minimum of seven keys, where each key corresponds to an individual braille point, except one key which is used as a spacebar. In some applications, the spacebar is used to produce additional chords which enable the user to issue editing commands, such as moving the cursor, deleting words, etc. Note that the number of points used in braille computing is not 6, but 8, as this allows the user, among other things, to distinguish between small and capital letters, as well as identify the position of the cursor. As a result, most newer chorded keyboards for braille input include at least nine keys.
Modern examples of chorded keyboards include the GKOS keyboard, the FrogPad and the EkaPad which are intended for tiny tablet PCs and wireless mobile terminals. The GKOS is basically a 6 keys Braille keyboard with a different signs and commands allocation of the 63 different chords in order to provide all PC keyboard functions and to make entering letters and numbers lighter by having to press fewer keys simultaneously. The 6 keys are intended to be on the back of the device and you operate with the 6 free fingers of two hands holding the device. The Frogpad exists as a bluetooth device and is somehow a half qwerty with a non qwerty disposition, claimed to be optimised for English.