Keyboard technology

The technology of computer keyboards includes many elements. Among the more important of these is the switch technology that they use. Computer alphanumeric keyboards typically have 80 to 110 durable switches, generally one for each key. The choice of switch technology affects key response (the positive feedback that a key has been pressed) and pre-travel (the distance needed to push the key to enter a character reliably). Virtual keyboards on touch screens have no physical switches and provide audio and haptic feedback instead. Some newer keyboard models use hybrids of various technologies to achieve greater cost savings or better ergonomics. The modern keyboard also includes a control processor and indicator lights to provide feedback to the user (and to the central processor) about what state the keyboard is in. Plug and play technology means that its "out of the box" layout can be notified to the system, making the keyboard immediately ready to use without need for further configuration, unless the user so desires. 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 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 produce a noticeable physical feedback.