Multi-Tech Systems MTA128ST-USB - Manual (Page 86)

86
MultiModemISDN User Guide
MTA128ST-USB
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, USB 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, amplitude, and/or
frequency to correspond with the source signal. Compare
with digital transmission.
API (application program interface)—A software module
created to allow dissimilar, or incompatible applications
programs to transfer 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 communications 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 operating 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.
basic access—A term that describes a simple
standardized combination 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 simultaneous 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
aggregation 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 implementations 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
multiplexing interoperability. It allows devices from various
manufacturers 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.