Multi-Tech Systems MTA128NT 用户手册

Symbol
2B1Q (2 bits, 1 quarternary)—A line code at layer one for the BRI
U interface. Two bits of data (2B) are mapped into one of four line
values (1Q, or 1quarternary). This coding scheme
allows a single copper pair to carry 160 Kbps of information
bidirectionally and simultaneously at a distance of up to three miles.

A
ACK (acknowledgement code)—A communications code sent from
a receiving modem to a transmitting modem to indicate that it is
ready to accept data. It is also used to acknowledge the error-free
receipt of transmitted data. Contrast with NAK.
address—A numbered location inside a computer. The computer
uses addresses to access resources such as video cards, serial ports,
memory, etc.
analog signal—A waveform that has amplitude, frequency, and
phase, which takes on a range of values between its maximum and
minimum points.
analog transmission—A type of telecommunications that uses an
analog signal as a carrier of voice, data, video, etc. An analog signal
becomes a carrier when it is modulated by altering its phase, ampli-
tude, and/or frequency to correspond with the source signal. Com-
pare with digital transmission.
API (application program interface)—A software module created
to allow dissimilar, or incompatible applications programs to trans-
fer information over a communications link. APIs may be simple or
complex; they are commonly required to link computer applications
with mainframe programs.
ASCII (American Standard Code for Information Interchange)—
Pronounced ass-key. A binary code for data that is used in communi-
cations and in many computers and terminals. The code is used to
represent numbers, letters, punctuation, and control characters. The
basic ASCII code is a 7-bit character set, which defines 128 possible
characters. The extended 8-bit ASCII code defines 255 characters.
ASI (application services interface)—A software module that creates
the interface between a LAN-connected PC and the network operat-
ing system. ASIs packetize computer data for transport over the
network. NASI, NCSI, MCSI and NETCI are specific examples.
AT commands—A standard set of commands used to control
modems. Each AT command string begins with the characters AT,
which get the attention of the modem before the actual command is
issued. See also command mode.

B
background—An activity that takes place in the computer while
you are running another application. In other words, the active user
interface does not correspond to the background task.
bandwidth—The transmission capacity of a computer channel,
communications line or bus. It is expressed in cycles per second
(hertz), the bandwidth being the difference between the lowest and
highest frequencies transmitted. The range of usable frequencies that
a transmission medium will pass without unacceptable attenuation or
distortion. Bandwidth is a factor in determining the amount of
information and the speed at which a medium can transmit data or
other information.
Bandwidth-on-Demand—Ability to request the amount of data

speed you need in any situation. Allows you to automatically add
and drop b-channels according to your preference; you pay only for
the bandwith you need.
basic access—A term that describes a simple standardized combina-
tion of access channels that constitute the access arrangements for
most ISDN users.
B-channel (bearer channel)—A 64 Kbps ISDN channel used for
digital high-speed data or voice transmission. Simultaneous voice
and data transmission requires subscription to two B-channels. A
voice call can be placed or received while a data call is in process
(or vice versa); however, two simultaneous voice or two simulta-
neous data calls are not supported.
bearer capability (BC)—The level of functionality provided by the
ISDN B-channel (e.g., data, 3.1 KHz audio, etc.).
bearer services—A set of ISDN functions provided by the B-
channel, such as digital telephony, toll-free inbound/outbound calls,
64 Kbps circuit switched data, X.25 packet switched data, and frame
relay data.
bit—A bit (binary digit) is a basic unit of information used in
computing and other digital electronics. It can take a value of either
1 or 0, represented in a computer by a high or low electrical charge.
BONDING (Bandwidth on Demand Interoperability Group)—An
inverse multiplexing method that combines multiple ISDN channels
into a single channel for enhanced throughput. Trademark of the
BONDING Consortium.
BONDING mode 1—An industry-standard ISDN B channel aggre-
gation protocol that was developed by the Bandwidth On Demand
Interoperability Group. This mode supports user data rates that are
multiples of the bearer rate. It provides the full available bandwidth,
but no in-band monitoring. Mode 1 is common to all implementa-
tions of BONDING; Modes 0, 2, and 3 are optional.
BONDING Consortium—A group that develops specifications for
common control and synchronization for management of high-speed
data over the public network.
BONDING Specification 1.0— The Version 1.0 BONDING
specification (August 1992) defines four modes of inverse multi-
plexing interoperability. It allows devices from various manufactur-
ers to subdivide a wideband signal into 64 Kbps or 56 Kbps
channels, and then pass the individual channels over a switched
digital network, recombining them into a single high-speed signal at
the receiving device.
BONDING Specification 1.1— The Version 1.1 BONDING
specification (September 1993) incorporates changes to the 1.0
specification resulting from interworking tests among various
vendors, and comments from the TIA standardization process. No
changes were made to the BONDING algorithm or procedures.
bps (bits per second)—The unit of speed at which data bits can be
transmitted or received. Bps differs from baud when more than one
bit is represented by a single cycle of the carrier.
BRI (basic rate interface)—Also called 2B+D. One of two forms of
ISDN service. BRI provides two 64 Kbps B-channels for video,
voice or data, and one 16 Kbps D-channel for control information.
The total BRI data rate is 192 Kbps, with 144 Kbps available to the
user. See also ISDN and PRI.
buffer—A temporary storage register or random access memory
(RAM), used in all aspects of data communications, that prevents
data from being lost due to differences in transmission speed.
Keyboards, serial ports, muxes and printers are a few examples of
devices that contain buffers.