A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding ball. The user rolls the ball to position the on-screen pointer, using their thumb, fingers, or commonly the palm of the hand while using the fingertips to press the mouse buttons.
Compared with a mouse, a trackball has no limits on effective travel; at times, a mouse can reach an edge of its working area while the operator still wishes to move the screen pointer farther. With a trackball, the operator just continues rolling, whereas a mouse would have to be lifted and re-positioned. Some trackballs have notably low friction, as well as being made of a dense material such as glass, so they can be spun to make them coast. The trackball's buttons may be situated to that of a mouse or to a unique style that suits the user.
Large trackballs are common on CAD workstations for easy precision. Before the advent of the touchpad, small trackballs were common on portable computers, where there may be no desk space on which to run a mouse. Some small "thumbballs" are designed to clip onto the side of the keyboard and have integral buttons with the same function as mouse buttons.
The trackball was invented as part of a post-World War II-era radar plotting system named Comprehensive Display System (CDS) by Ralph Benjamin when working for the British Royal Navy Scientific Service. Benjamin's project used analog computers to calculate the future position of target aircraft based on several initial input points provided by a user with a joystick. Benjamin felt that a more elegant input device was needed and invented a ball tracker system called the roller ball for this purpose in 1946. The device was patented in 1947, but only a prototype using a metal ball rolling on two rubber-coated wheels was ever built and the device was kept as a military secret. Production versions of the CDS used joysticks.
The CDS system had also been viewed by a number of engineers from Ferranti Canada, who returned to Canada and began development of the Royal Canadian Navy's DATAR system in 1952. Designed primarily by Tom Cranston, Fred Longstaff and Kenyon Taylor, they chose the trackball as the primary input, using a standard five-pin bowling ball as the roller. DATAR was similar in concept to Benjamin's display, but used a digital computer to calculate tracks, and sent the resulting data to other ships in a task force using pulse-code modulation radio signals.
DATAR's trackball used four disks to pick up motion, two each for the X and Y directions. Several rollers provided mechanical support. When the ball was rolled, the pickup discs spun and contacts on their outer rim made periodic contact with wires, producing pulses of output with each movement of the ball. By counting the pulses, the physical movement of the ball could be determined.
A similar trackball device at the German Bundesanstalt für Flugsicherung was constructed by a team around Rainer Mallebrein of Telefunken Konstanz as part of the development for the Telefunken computer infrastructure around the main frame TR 440, process computer TR 86 and video terminal SIG 100-86, which began in 1965. This trackball was called Rollkugel (German for "rolling ball"). Somewhat later, the idea of "reversing" this device led to the introduction of the first computer ball mouse (still named Rollkugel, model RKS 100-86), which was offered as an alternative input device to light pens and trackballs for Telefunken's computer systems since 1968.
In later trackball models the electrical contacts were replaced by a "chopper wheel" which had small slots cut into it in the same locations as the contacts. An LED shone light through the slots to an optical sensor, As the disk rotated the slots alternately lined up and then blocked the light from the LED, causing pulses to be produced in the sensor. The operation was otherwise similar.
Mice used the same basic system for determining motion, but had the problem that the ball was in contact with the desk or mousepad. In order to provide smooth motion the balls were often covered with an anti-slip surface treatment, which was, by design, sticky. Rolling the mouse tended to pick up any dirt and drag it into the system where it would clog the chopper wheels, demanding cleanup. In contrast the trackball is in contact only with the user's hand, which tends to be cleaner. In the late 1990s both mice and trackballs began using direct optical tracking which follows dots on the ball, avoiding the need for anti-slip surface treatment.
As with modern mice, most trackballs now have an auxiliary device primarily intended for scrolling. Some have a scroll wheel like most mice, but the most common type is a “scroll ring” which is spun around the ball. Kensington's SlimBlade Trackball similarly tracks the ball itself in three dimensions for scrolling.
As of 2013 two major companies produce consumer trackballs, Logitech and Kensington, although Logitech has narrowed its product line to two models. Other smaller companies occasionally offer a trackball in their product line. Microsoft produced popular models including The Microsoft Trackball Explorer, but has since discontinued all of its products.
Large trackballs are sometimes seen on computerized special-purpose workstations, such as the radar consoles in an air-traffic control room or sonar equipment on a ship or submarine. Modern installations of such equipment may use mice instead, since most people now already know how to use one. However, military mobile anti-aircraft radars, commercial airliners (such as Airbus A380) and submarine sonars tend to continue using trackballs, since they can be made more durable and more fit for fast emergency use. Large and well made ones allow easier high precision work, for which reason they may still be used in these applications (where they are often called "tracker balls") and in computer-aided design.
Trackballs have appeared in computer and video games, particularly early arcade games (see a List of trackball arcade games) notably Atari's Centipede and Missile Command – though Atari spelled it "trak-ball". Football, by Atari, released in 1978, is commonly misunderstood to be the first arcade game to use a trackball, but in The Ultimate History of Video Games by Steven L. Kent the designer of Football, Dave Stubben, claims they copied the design from a Japanese game, Soccer (Taito, 1973). Console trackballs, now fairly rare, were common in the early 1980s: the Atari 2600 and 5200 consoles, as well as the competing ColecoVision console, though using a joystick as their standard controller, each had one as an optional peripheral. The Apple Pippin, a console introduced in 1996 had a trackball built into its gamepad as standard. Trackballs were occasionally used in e-sports prior to the mainstreaming of optical mice in the early 2000s because they were more reliable than ball mice, but now they are extremely rare because optical mice offer superior speed and precision. A trackball requires no mousepad and enables the player to aim swiftly (in first person shooters). Trackballs remain in use in pub golf machines (such as Golden Tee) to simulate swinging the club.
Computer gamers have been able to successfully use trackballs in most modern computer games, including FPS, RPG, and RTS genres, with any slight loss of speed compensated for with an increase in precision. Many trackball gamers are competent at "throwing" their cursor rapidly across the screen, by spinning the trackball, enabling (with practice) much faster motion than can be achieved with a ball-less mouse and arm motion . However, many gamers are deterred by the time it takes to 'get used to' the different style of hand control that a trackball requires. Trackballs have also been regarded as excellent complements to analog joysticks, as pioneered by the Assassin 3D 1996 trackball with joystick pass-through capability. This combination provides for two-hand aiming and a high accuracy and consistency replacement for the traditional mouse and keyboard combo generally used on first-person shooter games. Many such games natively support joysticks and analog player movement, like Valve's Half-Life and id Software's Quake series.
Trackballs are provided as the pointing device in some public internet access terminals. Unlike a mouse, a trackball can easily be built into a console, and cannot be ripped away or easily vandalised. Two examples are the Internet browsing consoles provided in some UK McDonald's outlets, and the BT Broadband Internet public phone boxes. This simplicity and ruggedness also makes them ideal for use in industrial computers.
Because trackballs for personal computers are stationary, they may require less space for operation than a mouse, and may simplify use in confined or cluttered areas such as a small desk or a rack-mounted terminal. They are generally preferred in laboratory setting for the same reason.
An advantage of the trackball is that it takes less space to move than a mouse. A trackball was often included in laptop computers, but since the late 1990s these have switched to track pads. Track balls can still be used as separate input devices with standard desktop computers but this application is also moving to trackpads due to the prevalence of multi touch gesture control in new desktop operating systems.
People with a mobility impairment use trackballs as an assistive technology input device. Access to an alternative pointing device has become even more important for them with the dominance of graphically-oriented operating systems. There are many alternative systems to be considered. The control surface of a trackball is easier to manipulate and the buttons can be activated without affecting the pointer position.
Trackball users also often state that they are not limited to using the device on a flat desk surface. Trackballs can be used whilst browsing a laptop in bed, or wirelessly from an armchair to a PC playing a movie. They are also useful for computing on boats or other unstable platforms where a rolling deck could produce undesirable input.
Trackballs are generally either thumb-operated, with a ball about an inch in diameter or smaller moved by one digit (almost always the thumb) and the buttons clicked by others, or finger-operated, with a ball over two inches in diameter operated by the middle fingers and the buttons by the thumb and little finger. Users favour one format or another for reasons of comfort, mobility, precision, or because it reduces strain on one part of the hand/wrist. Most, but not all, finger-operated designs are symmetrical in design, making them usable by both hands, while thumb-operated designs are by their nature asymmetric or “handed,” allowing the smallest examples to be held in the air. Thumb-operated trackballs are not generally available in left-handed configurations, due to small demand.
Some computer users prefer a trackball over the more common mouse for ergonomic reasons. There seems to be no conclusive evidence from studies performed to determine which type of pointing device works best for most applications. Application users are encouraged to test different devices, and to maintain proper posture and scheduled breaks for comfort. Some disabled users find trackballs easier since they only have to move their thumb relative to their hand, instead of moving the whole hand, while others incur unacceptable fatigue of the thumb. Elderly people sometimes have difficulty holding a mouse still while double-clicking; the trackball allows them to let go of the ball while using the button.
At times when a user is browsing menus or websites rather than typing, it is also possible to hold a trackball in the right hand like a television remote control, operating the ball with the right thumb and pressing the buttons with the left thumb, thus giving the fingers a rest.
Some mobile phones have trackballs, including those in the BlackBerry range, the T-Mobile Sidekick 3, and many early HTC smartphones. These miniature trackballs are made to fit within the thickness of a mobile device, and are controlled by the tip of a finger or thumb. These have mostly been replaced on smartphones by touch screens.
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- For example, the Logitech Cordless Optical TrackMan is finger-operated but asymmetric.
- Center for Disease Control web page about computer ergonomics
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