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11
Glossary
AMTFT—
Acronym for Active Matrix Thin Film Transistor. This is the type of liquid crystal display panel used in
essentially all computer flat panel displays today.
Calibrate—
For touchscreens, “calibrate” is the common term for the process that is really “video alignment.”
A touchscreen and its controller have a coordinate system that is usually not identical to the coordinate system
of the video display of the host computer. By displaying reference points on the touch monitor (through the cali-
bration program) and touching those reference points, the touch monitor coordinate system is scaled to that of
the computer.
Color temperature—
Color temperature is a simplified way to characterize the spectral properties of a light
source, and is the temperature you would heat a theoretical “black body” source to radiate light of the same visual
color. For example, “low” color temperature, like 3200°K, implies warmer (more yellow/red) light, while “high” color
temperature, like 9300°K, implies a cooler (more blue) light. Daylight has the 3200°K temperature mentioned near
dawn and evening, and a higher one during the day. The standard unit for color temperature is the Kelvin (K).
Contrast Ratio—
The ratio of the luminance of the display of a full white image to a full black image. This
parameter is useful in determining the relative sharpness of two displays—a higher contrast ratio usually implies
a sharper image, especially when text is displayed.
Controller or Touchscreen controller—
The electronics that actually process the touch on the touchscreen and
sends out a digital representation of that touch to the host computer.
Emulation—
As used in display technology, emulation mode means an image displayed at a non-native resolution.
For your Aspen touch monitor and other 12" monitors, the common emulation mode is 640 x 480. In emulation
modes, a monitor cannot perfectly display the image sent from the computer when the monitor pixel to image
pixel ratio is not an integral multiple.
Hub or USB hub—
An electronic circuit that combines several USB signals into one.
Illuminance—
The measure of how much luminous flux per unit area that impinges on a particular surface, or
how bright a point source of light appears to the eye. It is measured in foot-candles or in lux.
Kelvin—
The scale of temperature measurement that begins at absolute zero. The increment of temperature that
one Kelvin represents is the same as that of the Celsius scale, but the scale starts at -273.16°C. Thus 293°K is
about 20°C or 68°F.
Keyboard emulation—
Produces the same output as a keyboard, or a “keyboard wedge” magnetic stripe reader.
Keyboard wedge—
An MSR unit that connects to a computer keyboard port with a cable that also connects the
standard keyboard, thus a keyboard wedge.
LCD—
Acronym for Liquid Crystal Display. The most common technology used in flat computer displays today.
“Liquid crystal” molecules (a very complex chemical engineered for this function) sandwiched between a combi-
nation of flat glass color filters and polarizers, pass or block light in response to electrical signals applied by the
display electronics. The result is a very sharp, bright display that is very thin, and uses little power, compared with
a CRT, or tube-type monitor.
Lux—
The standard unit for illuminance is lux (lx) which is lumens per square meter (lm/m2). 1lux = 10.764 foot-
candle. Common room lighting is 100-1000 lux.
MSR—
Acronym for Magnetic Stripe Reader. A device that reads information encoded in the magnetic stripes on
the back of a credit card, etc. The process is essentially identical to the operation of a cassette tape player.
