Multi-Tech MultiModem ISIHI-2S, Manual

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MultiModemISI Hybrid Series, ISIHI-2S 171
Glossary
Automatic Dialer: A device which is programmed to place
a call to a predetermined number any time it is taken “off-
hook”.
B
Background: An activity that takes place in the PC while
you are running another application. In other words, the
active user interface does not correspond to the ‘back-
ground’ task. In Windows™, the area behind the active
window. Compare with foreground.
Backup: Additional resources or duplicate copies of data on
different storage media for emergency purposes.
Band: The range of frequencies between two defined
endpoints.
Bandwidth: The transmission capacity of a computer
channel, communications line or bus. It is expressed in
cycles per second (hertz), the bandwidth being the differ-
ence between the lowest and highest frequencies transmit-
ted. The bandwidth of a phone line is about 3000Hz with
QAM, you get up to 14,400 bps. Bandwidth is often stated
in bits or bytes per second.
Baseband signal: An unmodulated signal which is trans-
mitted at its original frequency and may be digital or analog.
Baud: Rate, the signaling rate of a line, the switching
speed, or the number of transitions (voltage or frequency
changes) that are made per second. Transmission speeds
are often expressed in baud, though bits per second is
more accurate. The speed at which your computer talks to
your modem.
BCC (Block Check Character): An error control method
used in character-oriented or byte-synchronous protocols.
Two 8-bit BCCs are used to create the CRC (Cyclic Redun-
dancy Check) field of a synchronous data packet.
Bell 103: The U.S. modulation standard for 300 bps full-
duplex transmission over dial-up lines.
Bell 201: The U.S. modulation standard for 2400 bps half-
duplex transmission over dial-up lines or full-duplex trans-
mission over 4-wire lines. Primarily used in synchronous
modems.
Bell 202: The U.S. modulation standard for
0-1200 bps, half-duplex transmission over 2-wise, or full-
duplex transmission over 4-wire leased lines.
Bell 208: The U.S. modulation standard for 4800 bps, half-
duplex transmission over dial-up lines, or full-duplex trans-
mission over 4-wire lines. Primarily used in synchronous
modems.
Bell 212A: The U.S. modulation standard for 1200 bps full-
duplex transmission over dial-up lines.
Binary: A numbering system based on two digits, 1 and 0,
which is conductive to the two-state digital electronics used
within computers. All input to a computer is encoded as a
binary value. Binary also refers to a file format that uses 8-
bit characters , to allow for control characters (i.e., all non-
ASCII files).
BSC (Binary Synchronous Communications): Also
called “bisync”, this communications protocol was the first
synchronous data format used by IBM. It is still in use, but is
rapidly being replaced by IBM’s newer Synchronous Data
Link Control (SDLC). Bisync is a byte-synchronous protocol
that has longer delays and more overhead that the bit-
synchronous SDLC. It uses two synchronization characters
to head every packet.
Bit (Binary DigIT): A bit is the basis of the binary number
system. It can take the value of 1 or 0. Bits are generally
recognized as the electrical charge generated or stored by
a computer that represents some portion of usable informa-
tion.
Bit-synchronous transmission: A synchronous form of
data transmission that focuses on a maximum packet size
rather than the length of the characters the packet contains.
SDLC is a bit-synchronous protocol.
Boot: Starting or restarting your PC. This term originates
from the saying “to pull oneself up by the bootstraps”.
Bps (bits per second): A unit to measure the 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.
Break-out box: An electronic device which is inserted
between two RS232/V.24 connectors for the monitoring of
pin activity and for the re-routing of lines (crossover).
Broadcast: To send information simultaneously to a group
of recipients.
Buffer: A temporary storage register or Random Access
Memory (RAM), used in all aspects of data communications
which prevents data from being lost due to differences in
transmission speed. Keyboards, serial ports, muxes and
printers are a few examples of the devices that contain
buffers. A buffer allows one device to dump data at a high
speed and for the lower-speed device to accept it at its own
pace. In this way, the high-speed device can continue to
work without having to wait for its data transfer to end.
Buffers are a way of preventing potential data loss.
Bus: A common channel between hardware devices either
internally between components in a computer, or externally,
between stations in a communications network.
Byte: The unit of information a computer can handle at one
time. The most common understanding is that a byte
consist of 8 binary digits (bits), because that’s what comput-
ers (PCs) can handle. A byte holds the equivalent of a
single character, such as the letter “A”.