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U-90E Data/Fax Modem
modems to store settings and profiles. An EEPROM does not lose data when the modem is turned off.
EIA: Electronic Industry Association (of North America); this organization was the first to draft a standard
serial port (RS-232C).
EPROM: Electrically Programmable Read Only Memory. A memory chip which may be programmed
electronically, but must be exposed to ultraviolet radiation to be erased.
Error correction: A method to compensate for errors which occurred in the transmission path. Error
correction is done by the modems and is transparent to the DTEs. The most familiar correction methods
are MNP5 and V.42bis.
Fax: Long distance copy; facsimile - transfer of graphical data between two fax units. The graphical data is
compressed during transfer (G3).
FIFO-Buffer: First-in-first-out buffer. A buffer of this type is used in the 16550 type UARTs which allow
higher data throughput rates on PCs.
Firmware: The ZyXEL modems' system software is located in flash EPROMs. Depending on the size of
the EPROM(s), some features may or may not be available.
Flash: Memory designed for multi-purposes.
Flow control: Method to stop and start the data flow to avoid loss of data.
Front panel: The front panel on the ZyXEL modems consists of LED indicators and key switches.
Full-duplex: Transmission link where transmission can take place in both directions simultaneously.
FSK: Frequency Shift Keying - a frequency modulation scheme.
G3 fax: Several fax standards exist. Most available fax machines use the group 3 (G3) standard. This
standard defines the compression of graphic data and a transmission speed of up to 14400 bps with an
automatic fallback to 2400 bps if the telephone line is bad.
Handshake: At the beginning of a connection, the modems must negotiate and initialize the protocols to
be used and the speed at which the connection is to be established. This negotiation phase and the
following initialization phase is called handshake.
HDLC: High-level Data Link Control - protocol for synchronous transfer.
High-speed modem: A modem that works at bit rates higher than 9600 bps.
D
Glossary
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