Hardware Reference
In-Depth Information
The Windows and Application keys are not mandatory when running Windows. In fact,
preexisting standard key combinations can perform the same functions as these newer
keys.
The Windows keyboard specification requires that keyboard makers increase the number
of trilograms in their keyboard designs. A
trilogram
is a combination of three rapidly
pressed keys that perform a special function, such as Ctrl+Alt+Delete. Designing a key-
board so that the switch matrix correctly registers the additional trilograms plus the addi-
tional Windows keys adds somewhat to the cost of these keyboards compared to the pre-
vious 101-key standard models.
Manykeyboardmanufacturershavestandardizedon104-keykeyboardsthatincludethese
Windows-specific keys. Some manufacturers have added browser control or other keys
that, although not standard, can make them easier to use for navigating web pages and
launching various applications.
Foreign-language versions of the Windows keyboard include 105 keys and a slightly dif-
ferent layout from the 104-key U.S. versions.
For additional keyboard combinations you can use, see “Running Windows Without a
Mouse” in the Technical Reference section of the DVD included with this topic.
Keyboard Technology
The technology that makes up a typical PC keyboard is interesting. This section focuses
onalltheaspectsofkeyboardtechnologyanddesign,includingthekeyswitches,theinter-
face between the keyboard and the system, the scan codes, and the keyboard connectors.
Keyswitch Design
Today's keyboards use any one of several switch types to create the action for each key.
Most keyboards use a variation of the mechanical keyswitch. A mechanical keyswitch re-
lies on a mechanical momentary contact-type switch to make the electrical contact that
forms a circuit. Some high-end keyboards use a more sophisticated design that relies
on capacitive switches. This section discusses these switches and the highlights of each
design.
The most common type of keyswitch is the mechanical type, available in the following
variations:
• Pure mechanical
• Foam element
• Rubber dome
