ARQ - Automatic Repeat Request. A general term for error control
protocols featuring hardware detection and retransmission of
defective data. This term is used primarily by US Robotics.
ASCII - American Standard Code for Information Exchange. A 7-bit binary
code representation of letters, numbers and special characters.
It is universally supported in computer data transfer.
Asynchronous - Data transmission in which the actual data is preceded by a start
bit and followed by a stop bit since the time between transmitted
characters varies. Compare Synchronous.
Auto Answer - The modem feature which enables detection of a ring and answering
without assistance from a program.
Baud Rate - The number of discrete signal events per second occurring on a
communications channel. It is often referred to as Bits per
second (BPS) which is technically inaccurate but widely accepted.
BBS - Bulletin Board System.
Bit - Binary Digit. A single basic computer signal consisting of a
value of 0 or 1, off or on.
Buffer - A memory area used for temporary storage during input/output
Bulletin Board System - A host system, into which callers may dial with their modems to
read and send electronic mail, upload and download files, and
chat online with other callers.
Byte - A group of Bits acted upon as a group, which may have a readable
ASCII value as a letter or number or some other coded meaning to
the computer. It is commonly used to refer to 8-bit groups. 1
kilobyte = 1,024 bytes; 64K = 65,536 bytes or characters.
Carrier - A continuous frequency capable of being either modulated or
impressed with another information-carrying signal. Carriers are
generated and maintained by modems via the transmission lines of
the telephone companies.
Conference - An area of public messages on a Bulletin Board System, usually
with a particular topic and, often, a conference host or
moderator to guide the discussion. Also called Folder, SIG (for
"Special Interest Group") or Echo.
CCITT - A French acronym for the International Telephone and Telegraph
Consultative Committee. This international organization defines
the standards for telephone equipment such as the Bell 212A
standard for 1200 baud, CCITT V.22 for 2400 baud and CCITT V.32
for 9600 baud.
CPS - Characters Per Second. A transfer rate estimated from the bit
rate and length of each character. If each character is 8 bits
long and includes a start and stop bit for Asynchronous
transmission, each character needs 10 bits to be sent. At 2400
baud it is transmitted at approximately 240 CPS.
CRC - Cyclical Redundancy Check. An error-detection technique
consisting of a cyclic algorithm performed on each "block" of
data at the sending and receiving end of the transmission. As
each block is received, the CRC value is checked against the CRC
value sent along with the block. Many protocols including XMODEM-
CRC and ARQ will request a resend until the block is received
Download - Receiving a file from a Bulletin Board System, using a terminal
program (for example QModem) and a transfer protocol (for example
DTE - Data Terminal Equipment. The device that is the originator or
destination of the data sent by a modem.
DTR - Data Terminal Ready. A signal generated by most modems indicating
a connection between the DTE (computer) and the modem. When DTR
is "high" the computer is connected.
Data Compression Protocols - Compression of data by the modem allows more information to be
transferred in a shorter time frame. Protocols for data
compression include CCITT V.42bis and MNP 5.
Data Transmission Protocols - These are standards for modulation and transmission of data at
various speeds. The standards are Bell 103 & V.21 for 300bps,
Bell 212A & V.22 for 1200bps, V.22bis for 2400bps, V.32 for
9600bps and V.32 bis for 14,400bps. Proprietary protocols are
also used extensively for higher baud rates.
Echomail - Public Message Conferences on a Bulletin Board System which are
shared and distributed among other Bulletin Boards as part of an
Expanded Memory - Extra memory (above 640k) on your XT or AT-compatible computer,
which is installed with an EMS driver, and may be used by some
programs to store data.
Extended Memory - Extra memory (above 640k) on your 80286 or 80386 compatible
computer. Not normally usable by DOS applications, but may be
configured as a virtual drive or a disk cache on an 80286
computer, or as Expanded Memory on an 80386 computer.
Flow Control - A mechanism that compensates for differences in the flow of data
to and output from a modem or computer. Either hardware or
software can be used for this control to prevent data loss.
Hardware flow control using the modem makes use of a buffer to
store data to be sent and data received. Flow control is
necessary if the Communications port is locked at a higher rate
than the connection rate.
Error Control Protocols - These are various modem-based techniques which check the
reliability of characters or blocks of data at a hardware level.
Examples include MNP 2-4, V.42
Freeware - Computer software which may be distributed on Bulletin Board
Systems, and for which the author requests no license fee or
Full Duplex - Signal flow in both directions at the same time. It is sometimes
used to refer to the suppression of online LOCAL ECHO and
allowing the remote system to provide a REMOTE ECHO.
Half Duplex - Signal flow in both directions, but only one way at a time. It
is sometimes used to refer to activation of LOCAL ECHO which
causes a copy of sent data to be displayed on the sending
Host System - Another name for a Bulletin Board System (BBS)
Local Area Network (LAN) - A group of computers joined with cables and software, allowing
hard disks and other devices to be shared among many users.
Mail Door - A subsection of a Bulletin Board System which creates .QWK mail
MNP - Microcom Networking Protocol. A set of hardware error protection
protocols (MNP levels 1 - 4) and data compression techniques (MNP
level 5) developed by Microcom, now in the public domain. It
makes use of CRC and retransmission of defective blocks by
checking performed within the modem.
Netmail - Private electronic mail which is transmitted by a user calling
one Bulletin Board System to another user calling a different
Bulletin Board System.
NRAM - Nonvolatile Random Access memory. A user-programmable memory chip
whose data is retained when power to the chip is turned off. NRAM
is used in many modems to store default settings.
ON/OFF Hook - A descriptive term referring to manually lifting a telephone
receiver (taking it OFF Hook) and replacing it (going ON Hook).
OFF Hook produces a busy signal on the phone line.
Packer - A program to compress multiple files into a single file, such as
PKZIP, ARC or LHARC
Packet - A mail packet (with a .QWK extension) from a host system
Parity - An error detection method used in both communications and
computer memory checking to determine character validity.
Communications now makes use of more efficient "block" checking
although parity must still be matched in a communication session
for transfer to take place correctly. Host communication in the
BBS environment omits parity checking (no parity).
Protocol - A system of rules and procedures governing communications between
two devices. File transfer protocols in your communications
program refer to a set of rules governing how error checking will
be performed on blocks of data.
Public Domain - Computer software on which no copyright exists (usually by a
specific statement to that effect by the author), and which may
be freely used and distributed.
Remote Echo - A copy of the data being received is returned to the sending
system for display on the screen. See Full/Half duplex.
Shareware - Computer software which is distributed on the "Honor System",
which may be freely copied and distributed, but for which a
registration fee or payment is required for continued use beyond
an initial evaluation period.
SysOp - The SYStem OPerator of a Bulletin Board System. The person
responsible for setting up and maintaining the BBS.
Thread - A group of BBS messages and replies linked and sorted by topic.
Unpacker - A program to uncompress a file from a Packer
Upload - To transfer a file from your computer to another computer, using
your terminal program (for example Qmodem) and a transfer
protocol (for example Zmodem)
V.21 - CCITT standard for modem communications at 300bps. Modems made in
the US follow the Bell 103 standard.
V.22 - CCITT standard for modem communications at 1200bps, compatible
with the Bell 212A standard used in the US and Canada.
V.22 bis - CCITT standard for modem communications at 2400bps. It includes
automatic fallback to 1200bps and compatibility with Bell 212A
and V.22 modems.
V.23 - CCITT standard for modem communications at 1200bps with a 75bps
back channel. It is used in the United Kingdom.
V.32 - CCITT standard for modem communications at 4800 and 9600bps. It
includes automatic fallback to 4800 when line quality is poor.
v.34 -CCITT standard for modem communications at 28,800bps
V.32 bis - CCITT standard for modem communications at 14,400bps with
automatic fallback to 12,000, 9600, 7200 and 4800bps. As line
quality improves communications speed can also be increased to
the next higher rate.
V.42 - CCITT standard for modem communications that defines negotiation
for LAPM error control. V.42 also includes support for MNP error
correction protocol levels 1 - 4.
V.42 bis - CCITT extension of V.42 that adds data compression to the V.42