Pointing stick
A pointing stick (or trackpoint, also referred to generically as a nub or nipple) is a small analog stick used as a pointing device typically mounted centrally in a computer keyboard. Like other pointing devices such as mice, touchpads or trackballs, operating system software translates manipulation of the device into movements of the pointer on the computer screen. Unlike other pointing devices, it reacts to sustained force or strain rather than to gross movement, so it is called an "isometric"[1] pointing device. IBM introduced it commercially in 1992 on its laptops under the name "TrackPoint", and patented an improved version of it in 1997 (but the patent expired in 2017).[2] It has been used for business laptops, such as Acer's TravelMate, Dell's Latitude, HP's EliteBook and Lenovo's ThinkPad.
This article is about a computer input device. For the teaching and presentation aid, see Pointer (rod).
The pointing stick senses applied force by using two pairs of resistive strain gauges. A pointing stick can be used by pushing with the fingers in the general direction the user wants the pointer to move. The velocity of the pointer depends on the applied force so increasing pressure causes faster movement. The relation between pressure and pointer speed can be adjusted, just as mouse speed is adjusted.
On a QWERTY keyboard, the stick is typically embedded between the G, H and B keys, and the mouse buttons are placed just below the space bar. The mouse buttons can be operated right-handed or left-handed due to their placement below the keyboard along the centerline. This pointing device has also appeared next to screens on compact-sized laptops such as the Toshiba Libretto and Sony VAIO UX.
Design challenges[edit]
The IBM TrackPoint III and the TrackPoint IV have a feature called Negative Inertia that causes the pointer's velocity to "overreact" when it is accelerated or decelerated. Negative Inertia is intended to avoid the feeling of inertia or sluggishness when starting or stopping movement.[5] Usability tests at IBM have shown that it is easier for users to position the pointer with Negative Inertia, and performance is 7.8% better.[6]
Another challenge with pointing stick design is identification of the zero position (the position where no motion is desired). Because the amount of motion is small, the sensitivity of the sensors must be high, and they are subject to noise interference.
A typical solution, which assumes that pointing sticks frequently go out of calibration, is to interpret a variation below a certain threshold (over a given interval, perhaps one or several seconds) as being a neutral stick. However, the recalibration can also allow brief periods of 'drifting' (movement of the pointer while the user is not moving the pointing stick).[7]
In practice, if the re-calibration interval is set too short and if the user applies moderately consistent pressure to the stick for such an interval, this method results in an incorrect zero point. Additional pressure again moves the pointer, but the calibration may occur again, requiring even more force. If the user releases pressure at this point, the change will be interpreted as an instruction to move the opposite direction. In time, the software will re-calibrate and stop the motion.
Additionally, if "press-to-select" is enabled, the software may generate unexpected click events by touching the pointing stick during typing.
History[edit]
In 1984, Ted Selker, a researcher at PARC, worked on a pointing stick based on a study showing that it takes a typist 0.75 seconds to shift from the keyboard to the mouse, and comparable time to shift back. Selker built a model of a device that would minimize this time. It was only three years later, working at IBM, that Selker refined his design, resulting in the TrackPoint product[8] for which IBM received US patents in 1996[9][10] and 2000.[11]
Pointing sticks were the dominant pointing device for laptops before the advent of the touchpad. During later years, they faced a decline in popularity as most laptop-producing brands switched to touchpads, although as of 2021, some manufacturers like Lenovo still produce laptops with pointing sticks.[12]
Other uses[edit]
While typically employed on a computer keyboard, IBM included one on its Trackpoint Mouse product; suggested uses included scrolling (as with a scroll wheel) or a dual-cursor system.[26]