Touchpad

Its largest component is a tactile sensor: an electronic device with a flat surface, that detects the motion and position of a user's fingers, and translates them to 2D motion, to control a pointer in a graphical user interface on a computer screen.

Due to the ability of trackpads to be made small, they were additionally used on personal digital assistants (PDAs) and some portable media players.

Fingers insulated by a glove may also be problematic, and capacitive touchpads are rarely used as pointing devices for medical hardware.

Touchpad drivers can also allow the use of multiple fingers to emulate the other mouse buttons (commonly two-finger tapping for right click).

Xerox offered the Cat as an alternative input method for selecting strings of text to copy, delete, insert, or move around the document.

[10] Introduced a year later, in 1983, the first battery-powered clamshell laptop, the Gavilan SC included a touchpad, which was mounted above its keyboard, rather than below, which became the norm.

[11] Psion's MC 200/400/600/WORD Series,[12] introduced in 1989, came with a new mouse-replacing input device similar to a touchpad,[13] although more closely resembling a graphics tablet, as the cursor was positioned by clicking on a specific point on the pad, instead of moving it in the direction of a stroke.

Touchpads are primarily used in self-contained portable laptop computers and do not require a flat surface near the machine.

The touchpad is close to the keyboard, and relatively short finger movements are required to move the cursor across the display screen; while advantageous, this also makes it possible for a user's palm or wrist to move the mouse cursor accidentally while typing.

One-dimensional touchpads are the primary control interface for menu navigation on iPod Classic portable music players and additional input method on some Wacom digitizer tablets, where they are referred to as "click wheels", since they only sense motion along one axis, which is wrapped around like a wheel.

[citation needed] In the matrix approach, a series of conductors are arranged in an array of parallel lines in two layers, separated by an insulator and crossing each other at right angles to form a grid.

A high frequency signal is applied sequentially between pairs in this two-dimensional grid array.

If a ground point, such as the finger, is placed between the transmitter and receiver, some of the field lines are shunted away, decreasing the apparent capacitance.