Multitech MT5634HD16 User Manual page 73

transmitting data faster than normal, because the
acknowledgments are actually sent by the modem instead of
the remote UNIX computer.
Spooling (Simultaneous Peripheral Operations On-line):
Overlapping a low-speed operation with normal processing,
such as printing a file or document in the background while
creating a new document in the foreground.
SPX (Sequenced Packet Exchange): A data transport
protocol developed by Novell used for interprocess
communications. It guarantees that an entire message
arrives intact and uses the NetWare IPX protocol as its
delivery mechanism.
Switch Line: In communications, a physical channel
established by dynamically connecting one or more discreet
segments. This connection lasts for the duration of the call
after which each segment may be used as part of a different
channel. Contrast with leased line.
Switched Network:
A network in which a temporary connection is established
from one point via one or more segments.
Synchronous Transmission: The transmission of data
which involves sending a group of characters in a packet.
This is a common method of transmission between
computers on a network or between modems. One or more
synchronous characters are transmitted to confirm clocking
before each packet of data is transmitted. Compare to
Asynchronous Transmission.
T
T1 Transmission: A standard transmission speed of
1.544M bps that may be used in its full bandwidth, or as
narrower channels called "fractional T1" carriers.
TCM (Trellis Coded Modulation): An error correction
method that allows the receiving modem to tell if a signal
element is in error, based on the value of the preceding
signal elements. Each signal element is assigned a coded
binary value representing the element's phase and
amplitude.
Terminal: The screen and keyboard device used in a
centralized computing environment for interactive data
entry. Terminals have no "box", which is to say they have no
file storage or processing capabilities.
Terminal emulation: Allows a PC to access a mainframe
computer by generating and accepting data like a "dumb"
terminal.
Threshold: A value or condition which, when reached,
triggers an event.
Toggle: Alternate back and forth between two states.
CommPlete Communications Server
Tone dialing: One of two methods of dialing a telephone,
usually associated with push button phones. Compare with
pulse dialing.
Transistor: A semiconductor device used to amplify a
signal, or open and close a circuit. In digital computers, it
functions as an electronic switch.
TSR (Terminate and Stay Resident): A software program
that remains active and in memory after its user interface is
closed. Similar to a daemon in UNIX environments.
Twisted pair wiring: A type of cabling with one or more
pairs of insulated wires wrapped around each other. An
inexpensive wiring method used for LAN and telephone
applications, also called UTP wiring.
U
UART (Universal Asynchronous Receiver/Transmitter):
A chip that transmits and receives data on the serial port. It
converts bytes into serial bits for transmission, and vice
versa, and generates and strips the start and stop bits
appended to each character.
UNIX: A multi-user, multitasking operating system, first
developed by AT&T in the 1970's. It now runs on a wide
variety of computer systems from micro to mainframe, and
is controlled by UNIX System Laboratories (USL).
UTP (unshielded twisted pair): Telephone-type wiring.
V
V.21: The CCITT modulation standard for 300 bps, full-
duplex transmission over dial-up lines.
V.22: The CCITT modulation standard for 1200 bps, full-
duplex transmission over a dial-up or 2-wire leased line.
This is not common in North America.
V.22 bis : The CCITT modulation standard for 2400 bps, full-
duplex transmission over a dial-up or a 2-wire leased line.
V.23: The CCITT modulation standard for 75/1200 bps, half-
duplex transmission over dial-up lines. This is not common
in North America.
V.24: The CCITT hardware interface specification for
interchange circuits between the DTE and DCE.
V.25 bis : A dialing command set developed by the CCITT for
both synchronous and asynchronous devices. Since V.25 bis
does not provide any modem configuration commands, it is
primarily used for its synchronous dialing commands, while
the "AT" commands are used for asynchronous dialing and
for modem configuration.
V.26: The CCITT modulation standard for 2400 bps, full-
duplex transmission over 4-wire leased lines. Primarily for
synchronous use. Not common in North America.
Glossary
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