Input Devices - Upgrading and Repairing PCs - page 929

keyboards feature Ergo Technology, which has five levels of force from 35 grams to 80
grams,dependingontherelativestrengthofthefingersusedtotypevariouskeys.Aslittle
as 35 grams of force is required for keys that are used by the little finger, such as Q, Z,
and A, and greater levels of force are required for keys used by the other fingers (see Fig-
ure 15.5 ) . The spacebar requires the most force: 80 grams. This compares to the standard
force level of 55 grams for all keys on normal keyboards. For more information about
keyboardswithErgoTechnology,visittheKeyTronicEMSwebsite( www.keytronic.com ) .
Figure 15.5 Force levels used on KeyTronicEMS keyboards with Ergo Technology.
Perhapsthemostwell-knowntypeofmembranekeyboardsaretheIBM/Lexmark“Model
M” keyboards, which combine IBM's legendary buckling spring design with a high-end
membrane switch. To find the best membrane keyboards from the vast numbers on the
market, look at the lifespan rating of the keyswitches. Longer-lasting keyswitches make
the keyboard cost more but will lead to a better experience over the life of the keyboard.
Buckling Spring Capacitive and Membrane Switches
The keyboard included with the original IBM PC, XT, and AT systems used capacitive
switches combined with a buckling spring mechanism to provide the ultimate in perform-
ance and tactile feedback. Capacitive switches are technically the only truly nonmechan-
ical keyswitches in use today (see Figure 15.6 ). Although the movement of the key and
buckling spring is mechanical in nature, in the original designs these components do not
close a mechanical contact or switch. Because of the high cost of the capacitive switches,
IBM switched its buckling spring keyboards from capacitive to membrane switches in
the mid-1980s. However, unlike more common membrane keyboards, all buckling spring
keyboards feature extremely high-end designs. Regardless of whether capacitive or mem-
brane designs are used, buckling spring keyswitches are considered to be among the best
in the world, offering the highest-quality tactile feedback of any type of switch. They are