Multitech MMH900 User Manual page 186

B
Baud: Baud is rate, the signalling 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 BCC's
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 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 conducive to the two-
state digital electronics used within comput-
ers. 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).
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 differ-
ences 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 its 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 consists of 8
binary digits (bits), because that's what
computers (PCS) can handle. A byte holds
the equivalent of a single character (such as
the letter A).
C
Capacitor: An electronic device that stores
an electrical charge. It comes in varying sizes
for use in anything from power supplies to the
tiny cells in dynamic RAM chips. When the
device is powered down, it's capacitors lose
their charge.
Carrier signal: An analog signal with known
frequency, amplitude and phase characteris-
tics 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.
CCITT (Consultative Committee for
International Telephone and Telegraph):
An advisory committee created and controlled
by the United Nations and headquartered in
Geneva whose purpose is to develop and to
publish recommendations for worldwide
standardization of telecommunications
devices. CCITT has developed modem
standards that are adapted primarily by PTT
(post, telephone and telegraph) organizations
that operate telephone networks of countries
outside of the U.S..
Character set: One of a number of coding
schemes which uses binary digits to represent
characters, numbers, punctuation, and/or
control characters. Common character sets
are ASCII, ANSI or EBCDIC.
Checksum: A control field found in synchro-
nous data packets which contain the results of
the error control algorithm used.
Chip: Also called integrated circuits (IC), they
are squares or rectangles that contain from a
few dozen to a few million electronic compo-
nents.
Circuit: Any closed path through which
electrical current can flow.
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
the end-users multiplex the signals prior to
transmission.