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Appendix A • Glossary
Automation PC 820 User's Manual V 1.00
includes all functional, electrical and constructive conditions [encoding, signal level, pin
assignments] that characterize the connection point between the modules, devices, or systems.
Depending on the type of data transfer, a differentiation is made between parallel [e.g.
Centronics, IEEE 488] and serial interfaces [e.g. V.24, TTY, RS232, RS422, RS485], which are
set up for different transfer speeds and transfer distances. From the point of view of software,
the term "interface" describes the transfer point between program modules using specified rules
for transferring the program data.
ISA
An abbreviation for " I ndustry S tandard A rchitecture". A term given for the bus design which
allows expansion of the system with plug-in cards that can be inserted in PC expansion slots.
ISO
International Organization for Standardization > Worldwide federation of national
standardization institutions from over 130 countries. ISO is not an acronym for the name of the
organization; it is derived from the Greek word "isos", meaning "equal" (
www.iso.ch ).
Jitter
Jitter is a term that describes time deviations of cyclic events. If, for example, an event should
take place every 200µs and it actually occurs every 198 to 203µs, then the jitter is 5µs. Jitter has
many causes. It originates in the components and transfer media of networks because of noise,
crosstalk, electromagnetic interference and many other random occurrences. In automation
technology, jitter is a measure of the quality of synchronization and timing.
Jumper
A small plug or wire link for adapting the hardware configuration used to connect the different
points of an electronic circuit.
Keypad modules
Keypad modules are divided into two groups: Standard Keypad Modules (can be cascaded to
a controller) and Special Keypad Modules (must be connected by an electrician according to
the function e.g. Emergency Stop)
LCD
An abbreviation for " L iquid C rystal D isplay". A display type, based on liquid crystals that 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 that polarize the light passing through. A polarization
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