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MT5634HD8/16 User Guide
V.27: The CCITT modulation standard for 4800 bps, full or
half-duplex transmission. Primarily for synchronous use.
Not common in North America. V.27ter is used by Group 2
fax-modems for 4800 bps fax transmission.
V.29: The CCITT modulation standard for 9600 bps, 2-wire
(half-duplex) or 4-wire (full-duplex) transmissions,
primarily over leased lines (synchronous or asynchronous).
V.29 is used for Group 3 fax transmissions.
V.32: The CCITT modulation standard for synchronous or
asynchronous input to be transmitted at 9600 bps over the
PSTN. V.32 operates in half- or full-duplex mode.
V.32 bis : The CCITT modulation standard for synchronous
or asynchronous input to be transmitted at 14,400 bps over
the PSTN. V.32 bis operates in half- or full-duplex mode.
V.32terbo: An AT&T recommendation for synchronous or
asynchronous input to be transmitted at 14,400 bps over the
PSTN. V32terbo operates in half- or full-duplex mode.
V.32: The CCITT modulation standard for synchronous or
asynchronous input to be transmitted at 9600 bps over the
PSTN. V.32 operates in half- or full-duplex mode.
V.33: A CCITT modulation standard for 14,400 bps
synchronous transmission over a 40wire leased line.
V.35: The CCITT hardware interface specification commonly
used by DSU/CSUs and other high-speed devices.
V.42: A CCITT recommendation for error-control hardware
on a modem that accepts asynchronous input. V.42
recommends for manufactures to implement LAP-M and
makes a provision for MNP-5 as a alternative because of its
popularity. Most modem makers provide both.
V.42 bis : A CCITT recommendation for data compressing
hardware on a modem that accepts asynchronous input.
V.42 bis is based on a dynamically updated dictionary that
looks up common strings and replaces the strings with code
words. This reduces the amount of characters actually
transmitted. V.42 bis has been found to be most effective for
file transfers that contain long strings of repetitive
information and least effective for short strings of unique
data.
V.54: The CCITT recommendation to standardize Bit Error
Rate Testing (BERT) and Loopback testing (Local Analog
and Digital Loopback, as well as Remote Analog and Digital
Loopback).
VRC (Vertical Redundancy Check): An error checking
method that generates and tests a parity bit for each byte of
data that is moved or transmitted.
W
68
WATS (Wide Area Telephone Service): A discounted long-
distance calling plan that allows calls in or out. The popular
800 numbers are WATS lines in. The calls are charges to the
holder of the 800 number at a discounted rate.
Workstation: Traditionally a dumb terminal connected to a
host. However, with the advent of LANS and WANS, PCs that
are connected to a LAN are now called workstations too,
even though they are capable of independent processing. A
workstation is simply an input/display device through which
a user accesses a resource.
X
X.121: CCITT's recommendation for unique addressing of
each DTE connected to a communications network
throughout the world. X.121 uses fifteen digits: a one-digit
prefix, a four-digit DNIC number (which identifies the
country and PDN), and a ten-digit national terminal
number.
X.21: CCITT's recommendation for a 15-pin, digital
interface. It is not widely accepted, because of the analog
loops still prevalent in data communications. For this
reason, CCITT introduced the X21 bis standard for use with
synchronous modems.
X.25: CCITT's definition of a three-level packet-switching
protocol to be used between packet-mode DTEs and network
DCEs. X.25 corresponds with the lower three/four layers of
the seven layer OSI model.
X.28: CCITT's definition of asynchronous commands used
by a local ASCII terminal to configure an X.25 PAD.
X.29: CCITT"s definition of packetized commands sent to
configure a remote PAD via an X.25 link.
XModem: A widely used asynchronous file transfer
protocol. Programs typically use both the older version,
checksum, and the new version, CRC method, to detect
errors. If CRC is not present at the other end of a file
transfer, then it will use checksum.
Y
YModem: An asynchronous file transfer protocol that
improves speed by transmitting 1,024-byte (1K) blocks and
batch file transfer.
Z
ZModem: An asynchronous file transfer protocol that is
more efficient than XModem. It sends file name, date and
size first, and responds well to changing line conditions due
to its variable length blocks. It uses CRC error correction and
is effective in delay-induced satellite transmission.
CommPlete Communications Server
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