B&R Industries Provit 5000, Руководство пользователя

Страница: 372 / 400

Provit 5000 User’s Manual 371
Chapt
er
8
T
ec
hnic
al
A
p
pendix
Technical Appendix • Glossary
LCD
An abbreviation for »Liquid Crystal Display« A display type, based on liquid crystals which have
a polarized molecular structure and are enclosed between two transparent electrodes as a thin
layer. If an electrical field is applied to the electrodes, the molecules align themselves with the
field and form crystalline arrangements, which polarize the light passing through. A polarization
filter, which is arranged using lamellar electrodes, blocks the polarized light. In this way, a cell
(pixel) containing liquid crystals can be switched on using electrode gates, thus coloring this pixel
black. Some LCD displays have an electroluminescent plate behind the LCD screen for lighting.
Other types of LCD displays can use color.
LED
An abbreviation for »Light Emitting Diode« A semiconductor diode which converts electrical
energy into light. LEDs work on the principle of electroluminesence. They are highly efficient
because they do not produce much heat in spite of the amount of light they emit. For example,
"operational status indicators" on floppy disk drives are LEDs.
LPT
Logical device name for line printers. In MS DOS, names are reserved for up to three parallel
printer ports with the names LPT1, LPT2 and LPT3. The first parallel port (LPT1) is usually
identical to the primary parallel output device PRN (in MS-DOS the logical device name for the
printer). The lettering LPT was originally stood for "Line Printer Terminal".
LS-120
A disk drive which holds up to 120 MB on a 3.5" diskette. LS-120 drives can be also used for
other diskette formats.
Mkey
An abbreviation for »Module Keyblock«, a common term given to keys found on Provit display
units. They can be freely configured with Mkey utilities.
MTBF
An abbreviation for »Mean Time Between Failure« The average time which passes before a
hardware component fails and repair is needed. This time is usually expressed in thousands or
ten thousands of hours, sometimes known as power-on hours (POH).
MTC
An abbreviation for »Maintenance Controller« The MTC is an independent processor system,
which provide additional functions that are not available with a normal PC. The MTC
communicates with the PC via the ISA bus (using a couple register).