Multi-Tech Systems MTA128ST-USB - Manual (Page 87)

87
Glossary
MTA128ST-USB
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, USB ports,
muxes and printers are a few examples of devices that
contain buffers.
bus—A common channel between hardware devices,
either internally between components in a computer, or
externally between stations in a communications network.
byte—A unit of information consisting of eight binary digits
(bits). A byte holds the equivalent of a single or character
(such as the letter A).
C
call setup time—The time to establish a circuit-switched
call between two points. Includes dialing, wait time, and
central office–long distance service movement time.
carrier signal—An analog signal with known frequency,
amplitude and phase characteristics used as a transport
facility for useful information. By knowing the original
characteristics, a receiver can interpret any changes as
modulations, and thereby recover the information.
Centrex—A multi-line service, offered by telephone
companies, that provides functions and features
comparable to those of a PBX for large business users.
See also PBX, exchange.
channel—A data communications path between two
computer devices. It can refer to a physical medium (e.g.,
UTP or coax), or to a specific carrier frequency. In ISDN,
two types of channels are specified: transparent (user can
define the service), and nontransparent (service is
assigned protocols for specific network functions). ISDN
channel names are designated by a single letter, from A
through M, sometimes combined with a number (see B-
channel and D-channel).
circuit-switched network—A technology used by the
PSTN that allocates a pair of conductors for the exclusive
use of one communication path. Circuit switching allows
multiple conversations on one talk path only if end users
multiplex signals prior to transmission.
circuit switching—The temporary connection of two or
more communications channels using a fixed, non-
shareable path through the network. Users have full use of
the circuit until the connection is terminated.
CO (central office)—The lowest, most basic, level of
switching in the PSTN (public switched telephone
network). A business PABX or any residential telephone
connects to the PSTN at a central office.
COM port—A serial communications port on a personal
computer. Normally, there are two: COM1 and COM2.
CPE (customer premise equipment)—The generic term for
data communications and/or terminal equipment that
resides at the user site and is owned by the user (e.g., not
telephone company equipment).
D
DCE (data communications equipment)—Any device that
serves as the port of entry from the user equipment to a
telecommunications facility. A modem is a DCE for the
telephone network (PSTN) that is commonly on site at the
user’s premises. Packet Switched Networks have another
level of DCE that is most often located at a central office.
D-channel—A non-ransparent digital ISDN channel that
operates at 16 K or 64 Kbps, used for call control
signalling, along with one or more B-channels. The D
(demand) channel signal can control call setup, call
teardown, and invocation of Supplementary Services. Is
also used for telemetry and for low-speed, low-priority
packet-switched data. Contrast with B-channel.
default—A preset value or option in software packages or
in hardware configuration that is used unless you specify
otherwise.
default address: an address defined by the Universal
Serial Bus Specification and used by a Universal Serial
Bus device when it is first powered or reset. The default
address is 00h.
default pipe: the message pipe created by Universal
Serial Bus system software to pass control and status
information between the host and a Universal Serial Bus
device’s Endpoint 0.
device: a logical or physical entity that performs a function.
The actual entity described depends on the context of the
reference. At the lowest level, device may refer to a single
hardware component, as in a memory device. At a higher
level, it may refer to a collection of hardware components
that perform a particular function, such as a Universal
Serial Bus interface device. At an even higher level, device
may refer to the function performed by an entity attached
to the Universal Serial Bus; for example, a data/FAX
modem device. Devices may be physical, electrical,
addressable, and logical. When used as a non-specific
reference, a Universal Serial Bus device is either a hub or
a function.
device address: the address of a device on the Universal
Serial Bus. The Device Address is the Default Address
when the Universal Serial Bus device is first powered or
reset. Hubs and functions are assigned a unique Device
Address by Universal Serial Bus software.
device driver—Software that controls how a computer
communicates with a device, such as a printer or mouse.
digital data—Information represented by descrete values
or conditions (contrast analog data).
digital PBX—A private branch exchange that operates
internally on digital signals. See also exchange.
digital signal— A discrete or discontinuous signal (e.g., a
sequence of voltage pulses). Digital devices, such as as a
series of electrical pulses that have discrete jumps rather
than gradual changes.
digital transmission—A method of electronic information
transmission common among computers and other digital
devices. Because a digital signal may be only high or low
at any given time, noise and distortion can easily be
removed from digital transmissions.
digitize—To convert an analog signal to a digital signal.
DIP switch—Pronounced dip switch. A set of tiny toggle
switches, built into a DIP (dual in-line package), used for
setting configurable parameters on a printed circuit board.
DN (directory number)—The phone number assigned to an
ISDN TA at subscription time. It is a string of up to 24
characters, consisting of the valid dialing characters (0-9, *,
and #).