Multi-Tech Systems MTA128NT - Manual (Page 61)

Glossary
MTA128ST/NT 61
been approved by a regulatory group.
exchange area—A geographical area with a uniform set of charges
(tariffs), approved by a regulatory group for telephone services.
Calls between any two points within an exchange area are local
calls. See digital PBX and PBX.
F
fax (facsimile)—Refers to the bit-mapped rendition of a graphics-
oriented document (fax) or to the electronic transmission of the
image over telephone lines bit-mapped approximation of a graphical
document and, therefore, cannot be accurately interpreted according
to any character code.
firmware—Software that is stored in read-only memory (ROM).
Unlike random access memory (RAM), ROM can retain its content
without electrical power. Some ROM, known as EEPROM, can be
reprogrammed electrically while it is in a device.
foreground—The application program currently running on and in
control of the PC screen and keyboard. The area of the screen that
occupies the active window. Compare with background.
frequency—A characteristic of an electrical or electronic signal
which describes the periodic recurrence of cycles. Frequency is
inversely proportional to the wavelength or pulse width of the signal
(e.g., long wavelength signals have low frequencies and short
wavelength signals yield high frequencies).
H
handshaking—A process that two modems go through at the time
of call setup to establish synchronization over the data communica-
tions link. It is a synchronization and negotiation process accom-
plished by the exchange of predefined, mutually recognized control
codes.
HDLC (High-Level Data Link Control)—An ISO standard, bit-
oriented data communications protocol that provides nearly error-
free data transfers.
hexadecimal—A base 16 numbering system in which one character
represents a four-bit binary value. Hexadecimal notation uses the
numbers 0–9 and the letters A–F, usually suffixed by an h (e.g., 4CF
h).
I
IDN (Integrated Digital Network)—The culmination of transmission
and switching functions using digital technology in a circuit-
switched telecommunications network.
IEC (Inter-Exchange Carrier)—A telephone company that is al-
lowed to provide long distance telephone service between LATAs,
but not within any one LATA. Also called IXC.
IETF(Internet Engineering Task Force)—
A self-organized group of people who make technical and other
contributions to the engineering and evolution of the Internet and its
technologies. It is the principal body engaged in the development of
new Internet standard specifications.
I-mux (inverse multiplexer)—A device that will dial up and com-
bine several lower speed circuits into a virtual broadband circuit. It
takes any multiple up to an aggregate bandwidth, giving users
bandwidth on demand for videoconferencing, LAN-to-LAN connec-
tions, etc. In ISDN devices, inverse multiplexing is performed by the
BONDING protocol.
in-band signaling—A technique in which connection control
information is sent over the same channel as assigned to the sub-
scriber for end-to-end communication. Two common examples are
DTMF line signaling and MF trunk signaling.
Internet—A computer network consisting of many millions of
university, government, and private users around the world.
Internet address—A unique 32-bit address for a specific TCP/IP
host on a network. Normally printed in dotted decimal format (e.g.,
129.128.44.227).
I/O address—A location within the I/O address space of your
computer used by a device, such as an expansion card, a serial port,
or an internal modem. The address is used for communication
between software and a device.
IP address—A unique 32-bit address for a specific TCP/IP host on a
network. Normally printed in dotted decimal format (e.g.,
129.128.44.227).
IRQ (interrupt request)—The notification a processor receives when
another portion of the computer’s hardware requires its attention.
IRQs are numbered so that the device issuing the IRQ can be
identified, and so that IRQs can be prioritized.
ISA (Industry Standards Architecture)—Pronounced ice-a. The
classic 8- or 16-bit architecture introduced with IBM’s PC-AT
computer. Due to speed constraints, IBM later introduced a restruc-
tured Micro Channel Architecture with a 32-bit bus and increased
addressing capabilities.
ISDN (Integrated Services Digital Network)—International telecom-
munications standard for transmitting voice, video and data over a
digital communications line.
ITU-T (formerly CCITT)—International Telecommunications
Union–Telecommunications Sector; the United Nations organization
that prepares standards for resolving communications issues and
problems.
L
LAPB (Link Access Procedure Balanced)—Based on the X.25
Layer 2 specification. A full-duplex, point-to-point, bit-synchronous
protocol commonly used as a data link control protocol to interface
X.25 DTEs. LAPB is the link initialization procedure that estab-
lishes and maintains communications between the DTE and the
DCE.
LAPD (Link Access Protocol for the
D-Channel)—Based on the ISDN Q.921 specification. A full-duplex
point-to-point bit-synchronous link-level protocol for ISDN connec-
tions; different from LAPB in its framing sequence. Transmission is
in units called frames, and a frame may contain one or more X.25
packets.
link optimization—An ISDN feature that permits only user data to
open the communications link and keeps administrative packets
from opening the link. A cost saving feature that ensures that remote
connections are not unnecessarily utilized.
local loop—A transmission path, typically twisted-pair wire, be-
tween an individual subscriber and the nearest public telecommuni-
cations network switching center. Also called the subscriber loop.
LT (loop termination)—A device, similar to an NT1, that terminates
the local loop at the carrier’s central switching office. The LT
provides the interface to the ISDN U reference point. Contrast ET
(exchange termination).
M
MD5(MD5 Message-Digest Algorithm)—Takes a message if
arbitrary length as input and produces it as output as a 128-bit
fingerprint or message digest of the input. The MD5 algorithm is
used for digital signature applications where a large file must be