Keyboard technology

related topics
{system, computer, user}
{@card@, make, design}
{acid, form, water}
{ship, engine, design}
{line, north, south}
{theory, work, human}

There are many types of keyboards, usually differentiated by the switch technology employed in their operation. Since there are so many switches needed (usually about 80-110) and because they have to be highly reliable, this usually defines the keyboard. The choice of switch technology affects key response (the positive feedback that a key has been pressed) and travel (the distance needed to push the key to enter a character reliably). Newer models use hybrids of various technologies to achieve greater cost savings.

Contents

Types

Membrane keyboard

There are two types of membrane-based keyboards: Flat-panel membrane keyboards and full-travel membrane keyboards:

Flat-panel membrane keyboards are most often found on appliances like microwave ovens or photocopiers. A common design consists of three layers. The top layer (and the one the user touches) has the labels printed on its front and conductive stripes printed on the back. Under this it has a spacer layer, which holds the front and back layer apart so that they do not normally make electrical contact. The back layer has conductive stripes printed perpendicularly to those of the front layer. When placed together, the stripes form a grid. When the user pushes down at a particular position, their finger pushes the front layer down through the spacer layer to close a circuit at one of the intersections of the grid. This indicates to the computer or keyboard control processor that a particular button has been pressed.

Generally, flat-panel membrane keyboards do not have much of a "feel", so many machines which use them issue a beep or flash a light when the key is pressed. They are often used in harsh environments where water or leak proofing is desirable. Although used in the early days of the personal computer (on the ZX80, ZX81 and Atari 400), they have been supplanted by the more tactile dome and mechanical switch keyboards. However, membrane keyboards with interchangeable key layouts, such as the IntelliKeys and Discover:board are still commonly used by people with physical, visual, or cognitive disabilities as well as people who require assistive technology to access a computer.

Full article ▸

related documents
Electrical connector
Stereo 8
Switch
Computer-aided design
Potentiometer
Magnetic core memory
SECAM
Screensaver
Video compression
Insulated-gate bipolar transistor
NAPLPS
Router
Digital Imaging and Communications in Medicine
Graphical Environment Manager
Public land mobile network
Windows Media Audio
MAME
High-Level Data Link Control
Spread spectrum
Blitter
Microkernel
IBM System i
Software performance testing
Xerox Star
Frequency-hopping spread spectrum
Trillian (software)
Amateur radio
Altair 8800
Pixel
Video game console