Most QWERTY computer keyboards use a single rubber-like membrane underneath the keys that makes contact with a circuit board when the key is fully depressed. Also called a "dome switch keyboard," this style is also found on many types of keypads. There is less tactile sensation from membrane keyboards than there is when individual key switches are used (see mechanical keyboard
The Dome Switch Keyboard
Widely used, the membrane is sculpted with a raised dome for each key.
A keyboard that tolerates dirt and spillage that would otherwise cause a regular keyboard to fail. Membrane keyboards use a flexible plastic sheet printed with the key pattern on top and electrically conductive ink on the underside. When a key is pressed, it pushes the top layer down through a spacer layer of holes and makes contact with the circuit at the bottom. Widely used in self-service applications, there may be little movement in the keys, and a beep or LED is often used for feedback.
A Rugged Terminal for Point-of-Sale (POS)
Although membrane keyboards may come in standard QWERTY layouts, they are often designed for specific applications as in this example. (Image courtesy of Polytel Computer Products Corporation.)
Customizable Membrane Keyboard
IntelliKeys uses a base unit divided into a 24x24 cell matrix, and removable keyboards are printed with Overlay Maker software. Developed for adults and children with disabilities, IntelliKeys are also used for business. (Image courtesy of Synapse Adaptive, www.synapseadaptive.com)