Chiclet keyboard

Rubber keyboard from a remote control. When the key is pushed down, the conductive material on its underside touches the pair of fork-shaped traces below, bridging the gap between them and closing the circuit.

A chiclet keyboard is slang for a computer keyboard built with an array of small, flat rectangular or lozenge-shaped rubber or plastic keys that look like erasers or pieces of chewing gum. The term comes from "Chiclets", the brand name of a variety of chewing gum.

Manufacturers liked the chiclet keyboard because it was cheap to produce, and many early home computers (notably the ZX Spectrum), portables and laptop computers were launched with it. However, consumers rejected it with almost equal unanimity, even though it was not quite as unpleasant to work with as the membrane keyboard. Since the mid-1980s, chiclet keyboards have been mainly restricted to lower-end electronics, such as small handheld calculators, cheap PDAs and many remote controls.

The expression "chiclet keyboard" is not common to every country. For example, in the UK (where Chiclets gum is not sold), it is more often referred to as either a dead-flesh keyboard (from the feel of the keys) or simply a rubber-keyed keyboard. In Norway, the term eraser keyboard was commonly used (from the keys' likeness to pencil erasers).

See also: keyboard technology

How it works

In some (but not all) versions of the chiclet keyboard, the bottom three layers are essentially the same as those in the membrane keyboard. In both cases, a keypress is registered when the top layer is forced through a hole to touch the bottom layer. For every key, the conductive traces on the bottom layer are normally separated by a non-conductive gap. Electrical current cannot flow between them; the switch is open. However, when pushed down, conductive material on the underside of the top layer bridges the gap between those traces; the switch is closed, current can flow, and a keypress is registered.

Unlike the membrane keyboard, where the user presses directly onto the top membrane layer, this form of chiclet keyboard places a set of moulded rubber keys above this. With some key designs, the user pushes the key, and under sufficient pressure the thin sides of the rubber key suddenly collapse. In other designs- such as that seen in the diagram- the deliberate weak-point is where the key joins the rest of the sheet. The effect is similar in both cases, however.

This collapse allows the solid rubber center to move downwards, forcing the top membrane layer against the bottom layer, and completing the circuit.

The "sudden collapse" of the chiclet keyboard (along with the movement of the key) provides a greater tactile feedback to the user than a simple flat membrane keyboard.

Stylised cross-section of a Chiclet keyboard. The thickness of the bottom three layers is exaggerated for clarity; in real-life they are not much thicker than paper. Note the distortion of the thin rubber where the right-hand key (pressed) joins the sheet. Some designs omit the top membrane (green) and hole (black) layers, instead coating the undersides of the keys themselves with conductive material (red).

Other versions of the chiclet keyboard omit the upper membrane and hole/spacer layers; instead the underside of the rubber keys themselves have a conductive coating. (This is the type shown in the photograph of the remote control, above). When the key is pushed, the conductive underside makes contact with the traces on the bottom layer, and bridges the gap between them, thus completing the circuit.

The dome switch keyboards used with a large proportion of modern PCs are technically similar to chiclet keyboards. However, the rubber keys are replaced with rubber domes, and hard plastic keytops rest on top of these.

List of notable computers with chiclet keyboards

Most of the computers listed hail from the early home computer era.

• Cambridge Z88 (arguably a mix between a membrane and chiclet keyboard)
• Commodore PET 2001 (the original 1977 PET) had the square keys of a calculator or cash register.
• Commodore 116 (version of the C16 sold only in Europe)
• IBM PCjr
• Jupiter ACE
• Mattel Aquarius
• Microdigital TK 90X (Brazil ZX Spectrum derivation)
• Multitech Microprofessor I (MPF 1) and MPF II (the latter an early Apple II compatible)
• Oric 1
• Panasonic JR-200
• Sinclair ZX Spectrum 16/48K (later models had slightly improved keyboards)
• Sharp MZ-80K
• Spectravideo SV-318
• Tandy TRS-80 Color Computer I (later 'CoCo's had full-travel keyboards)
• Tandy TRS-80 MC-10 and its French counterpart, the Matra Alice
• Texas Instruments TI-99/4 (predecessor of the TI-99/4A, which had a full-travel keyboard)
• Timex Sinclair 1500 (U.S. ZX81 derivation)
• Timex Sinclair 2068 (U.S. ZX Spectrum derivation)
• VTech Laser 200 (also known as the Video Technology VZ200)
• Some early models of MSX computers, for example the Philips VG-8010

References and footnotes

1. http://www.notebookreview.com/default.asp?newsID=3780

External links

• Google Image Search for Chiclet Keyboard

This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.