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- A networking standard that utilizes UTP cabling with RJ-45 connectors,
and transfers data at up to 10 Mbps. It has the advantage of utilizing
economical and easy-to-install cabling.
- A networking standard that transfers data at up to an amazing 100 Mbps,
and utilizes UTP cabling with RJ-45 connectors.
- Original Ethernet using coaxial cable.
- A networking standard that utilizes thin coaxial cabling with BNC
connectors, and transfers data at up to 10 Mbps. It has the advantage of
utilizing cabling with longer maximum lengths (610.5" as opposed to 330"
with 10BaseT cabling).
- A technology that allows a serial port to transmit compressed data at up
to 115.2 Kbps.
- A technology that allows a serial port to transmit compressed data at up
to 460.8 Kbps.
- Defined by the IEEE (Institute of Electrical and Electronics Engineers),
these standards regulate the use of the CSMA/CD (Carrier Sense Multiple
Access/Collision Detection network access method used by Ethernet networks.
- The number of bits which represent each pixel, or point on the screen. An
8-bit per pixel card can generate 256 colors; 24 bits per pixel yields 16.8
- An IBM color monitor capable of resolutions of 720x400 non-interlaced with
a refresh rate of 70MHz; 640x480 non-interlaced at 60MHz; or 1024x768 interlaced
at 43.58 MHz. All of these resolutions are in 256 colors.
- A formula or procedure which employs various methods defining how data is
to be used to give a prescribed result.
- The variation in a sound signal producing varying levels of loudness.
Measured in decibels (dB).
- Analog Signals
- Signals which can vary over a continuous range (e.g., the human voice over
conventional telephone lines). Analog circuitry is more subject to distortion
and noise, but it is more capable of handling complex signals than are digital
signals which can have only discrete values.
- Analog Sound
- Recorded sound depicted by fluctuations in amplitude.
- Automatic ReQuest for retransmission. A type of communications link where
the receiver asks the transmitter to re-send a block of data when errors are
- American National Standards Institute. A non-profit, private industry
association which governs most USA-standards setting agencies.
- Acronym for American Standard Code for Information Interchange. ASCII is an
ANSI character set. The standard ASCII character set consists of 128 decimal
numbers (0-127) for letters of the alphabet, numerals, punctuation marks, and
common special characters. The extended ASCII character set extends to 255
characters and contains special mathematical, graphics, and foreign characters.
- Asynchronous Communications
- A method of transmission in which one character is sent one bit at a time;
also referred to as serial transmission.
- AUI connector
- A networking connector that can be used with a transceiver to connect
various kinds of cables such as fiber optic (10BaseF), thick coaxial
(10Base5), thin coaxial (10Base2) and UTP (10BaseT).
- auto-switching power supply
- An electrical plug that will work internationally in 110-, 220- or
230-volt outlets by automatically detecting the current and using the
- Bell standards
- Refers to the U. S. modulation protocol standards developed by the former
AT&T Bell Systems such as Bell 103 (300bps transmission) and Bell 212A
- Basic Input Output System. Provides fundamental services required for the
operation of a computer. Permanently present in the machine, these routines are
generally stored in ROM (Read Only Memory). The system board contains a ROM BIOS
to support all of its standard functions. The Voyager Movie Player also has a
BIOS for display features.
- Bit Block Transfer
- A method of holding a block of graphics, such as Windows dialogue box, in
memory so that it can be moved and redrawn quickly by memory-to-memory
- Bit-mapped Registers
- An S-register which contains multiple bit-oriented values.
- Blind Dialing
- An automated process whereby the modem goes off-hook and dials without
waiting for a dial tone. This is prohibited in many countries.
- Block Transfer Control
- Determines whether or not the modem uses block or stream mode during an MNP
connection. In stream mode, MNP sends data frames in varying length. Block mode
sends fixed data frames of 256 characters.
- BNC connector
- A connector utilized in 10Base2 networks with thin coaxial cabling.
- Boot PROM
- (Boot Programmable Read-Only Memory). A ROM chip usually mounted on the
network interface card that enables a personal computer to load the operating
system from the network.
- Bits per second.
- Break Handling
- Determines how the modem responds when a BREAK signal is received from
either the DTE (Data Terminal Equipment or computer/terminal) or the remote
modem. This is controlled by the MNP-based AT extended commands. A break signal
is represented on the communications line by a steady space signal for a
significant length of time. Break signals may be activated from the keyboard by
pressing the BREAK key or the control (CTRL) and C keys.
- Bus topology
- A network topology in which nodes are connected to a single cable with
terminators at each end.
- Consultative Committee for International Telephone and Telegraph. This
advisory organization is part of the ITU (International Telecommunication Union)
which is an agency of the United Nations. Organization recently renamed
International Telecommunications Union-Telecommunications Standard Sector
- CD Quality
- Recording quality similar to that of a compact disc player. This means that
16 bits of information are recorded for every sample taken. See Bits Per Sample
- Color Graphics Adapter. Medium resolution IBM graphics standard capable of
displaying 640 x 200 pixels in 2 colors, or 320 x 200 pixels in 4 colors.
- Coaxial Cable
- Data transmission medium with a single-wire conductor insulated from
electro-magnetic and radio frequency interference.
- Command Mode
- The modem is in command mode when it is turned on or reset, when it loses
its connection to a remote modem, when it is in on-line mode, or when escape
characters (+++) are typed. To transmit data, the modem must be in data mode.
The modem does not transmit data when in command mode.
- Communications Protocol
- A set of procedures which controls how a data communications network
- See hub.
- Carrier Sense Multiple Access with Collision Detection. CSMA/CD is the
access method used in Ethernet where nodes contend for the right to send data.
- Data Carrier Detect. Indicates to the terminal device that the modem is
receiving a valid carrier signal from a remote modem. The carrier is a tone at a
- Data Communications Equipment. The local and/or remote modem. A DCE is
usually connected to a DTE.
- Direct Memory Access. DACK stands for Dma ACKnowledge and DRQ for Dma
ReQuest. DMA provides direct access to system memory without adding to CPU
overhead. The DACK and DRQ channels govern that communication.
- Data Terminal Equipment. The computer or terminal, either local (yours), or
the remote (the one you're communicating with). A DTE is usually connected to a
- Dynamic RAM. RAM is random access memory.
- Data Terminal Ready. The computer issues this signal to the attached modem
indicating that it is ready to receive data.
- Data Compression
- A technique that examines transmitted data for redundancy and replaces
strings (groups) of characters with special codes which the receiving modem
interprets and restores to its original form. Transmission of compressed data
results in shorter connect times and hence cost savings for connect charges.
Data compression is sometimes called "source encoding".
- Data Mode
- The modem is in data mode when a connection has been established with a
remote modem and sends a CONNECT response confirming the connection. User data
may then be transmitted or received.
- Decibel (dB)
- A means of measuring amplitude.
- Dial Modifier
- Dial modifiers are special characters appended to the ATD command which
instruct the modem how to place a call.
- Digital Signal
- A discrete signal which can only take on one of several (usually only two)
discrete levels in contrast to analog signals which can take a continuous range
- Digital Sound
- Recorded and stored sound as a series of numerical values rather than
fluctuations in amplitude.
- dual-line modem
- A modem with two 56K modem chips on a single board that connects to two
regular phone lines and utilizes bonding software to offer transmission
speeds of up to 112 Kbps.
- Enhanced Color Display. An EGA specification. TTL monitor capable of
displaying video signals with horizontal scan frequencies of 15.750KHz (CGA) or
21.850KHz (EGA) only.
- Enhanced Graphics Adapter. High resolution IBM graphics standard capable of
displaying 640 x 350 pixels in 16 colors out of a palette of 64 colors.
- Error Detection and Correction.
- The transmitting modem attaches a special pattern (called a frame check
sequence) calculated according to a prescribed algorithm from user-defined data
to the end of a block of data. The receiving modem performs the same algorithm
and compares it to the one with the transmitted data. If these match, then the
block of data has been received correctly. If not, the block of data is
re-transmitted until no errors are detected.
- Escape Sequence
- Also referred to as the escape command. This special command is entered as
three plus symbols (+++) and places the modem in command mode and interrupts
user data transmission, but does not terminate the data connection. This allows
the entering of commands while the connection is maintained.
- A 10 megabits-per-second baseband, CSMA/CD network originally designed by
the Xerox Corporation.
- Extended AT-Command
- Extended commands were developed to provide greater functionality and
control over modem operations than is available from the basic AT command set.
- Fax Mode
- The modem is in fax mode when, through use of fax communications software,
it can send and receive faxes, print and display fax files, convert files to
fax-files, and set certain fax-related features. Note: the modulation protocol
used by the modem in fax mode is also different from the usual data mode
- Feature Connector
- Used by graphics adapters to give compatibility with VGA text and graphics
codes for use with multi-media applications.
- File Server
- A device on a LAN that provides mass storage of files. A file server can be
dedicated (only performs network management functions) or non-dedicated (where
user applications can co-exist while the network is available.
- Flow Control
- Compensates for the difference between the rate at which data reaches a
device and the rate at which the device processes and transmits. The two common
types of flow control are RTS/CTS signaling (a hardware based method, employing
an electrical signal) and XON/XOFF (a software-based method using standard ASCII
control characters to pause or resume transmission). The \G command controls
XON/XOFF flow control.
- full duplex
- The ability to send and receive data at the same time. (A full duplex
speakerphone allows you to hear what is going on at the other end of the
line while you are talking.)
- Guard Tone
- Guard tones are used in the United Kingdom and other countries. This
requires that the modem transmit an 1800-Hz tone after it sends an answer tone.
The guard tone is controlled by the &G command. Guard tones are not used in
- Graphical User Interface.
- half duplex
- The ability to send data in only one direction at a time.
- Hayes Microcomputer Products, Inc. developed the AT command set which has
become a de facto industry standard. Hayes commands are always initiated with an
AT (attention code) prefix.
- Hardware Graphics Cursor
- Provides a faster method of displaying/moving a cursor (GUI arrow) on the
screen. The video adapter's main chipset controls this function which resides in
system memory, as opposed to slower handling by the application software.
- Hercules Graphics Card. Compatible with MDA, but also capable of displaying
720 x 348 pixels in a 4-bank graphics mode.
- Short for High Resolution, this term should be only applied to a minimum of
640 x 350 resolution and above.
- Hook Flash
- The dial modifier "!" causes the modem to go on-hook (hang-up)
for one-half second. Also controlled by the ATH command.
- Horizontal Scan Rate
- The frequency in KHz (kilohertz) at which the monitor is scanned in a
horizontal direction; high horizontal scan rates produce higher resolution. The
EGA horizontal scan rate is 21.8 KHz, while the extended EGA horizontal scan
rate is 30.1 KHz.
- A networking device with multiple ports that allows you to connect
workstations, servers or peripherals to a network.
- IEEE 802.3 compliant
- Complying to the standards for 10 Mbps networks established by the
Institute of Electrical and Electronic Engineers (IEEE)
- A method of scanning a screen which results in alternate lines being drawn
with each full pass of the electron beam. The resulting display is less stable
than a flicker-free non-interlaced display.
- I/O card
- An abbreviation for input/output card. A board in your PC with a serial
or parallel port that allows you to connect peripherals to your
computer. I/O cards can also have multiple serial or parallel ports or a
combination of both.
- This occurs when there are excessively long data packets being transmitted
from the node (i.e., workstation, server). At that point, the hub, or
concentrator, partitions (isolates) the node from the network until the
condition is corrected.
- jabber protection
- A feature of some networking hubs that ensures your network won't go
down due to excessively long data packets.
- A set of tiny switches used to select one of various options such as a
particular hardware configuration.
- An abbreviation for kilobits per second. A measurement of the
transmission speed of data measured in 1,024 bits per second.
- (Local Area Network) A data communications network confined to a limited
geographic area, with moderate to high data rates (100kbps to 100Mbps). The
area served may consist of a single building or campus-type arrangement. It is
owned by it's use, includes some type of switching technology, and does not use
common carrier circuits - although it may have gateways or bridges to other
public or private networks.
- Link Access Protocol Modem. A V.42 ARQ type of error correction protocol
where LAPM may be activated with or without V.42bis data compression.
- Leased Line
- Also referred to as a private line. A leased line is obtained from a
communications company (carrier) to provide a transmission medium between two
points. The line consists of a permanent dedicated circuit between two points,
or to set of previously arranged points. The cost of the line is usually based
on the distance between locations. This is in contrast to switched or dial-up
lines, which can be connected to any point on the network.
- Light-emitting diode.
- Line Modulation
- The means by which a carrier is varied to represent a signal carrying
information. In a modem, the user's digital data is used to modulate the modem's
transmitter's carrier or carrier to allow the digital signal to be carried over
- A connector on audio equipment to which a device like a CD-player or tape
cassette player may be attached. See also Line Out.
- A connector on audio equipment to which audio components can be attached
such as stereo speakers. See also Line In.
- Long Space Disconnect
- Determines whether or not modem disconnects when it receives a continuous
break from a remote modem. Controlled by the ATY command.
- Loopback Tests
- There are four types of loopback tests which are as follows: (1) the local
digital loopback tests the operation of the DTE, including whether or not data
is leaving the terminal or computer port; (2) the local analog loopback tests
the digital and analog circuits of the modem; (3) the remote digital loopback
checks the operating condition of the line and remote modem; (4) the remote
analog loopback tests the line to the remote modem.
- Make/Break Ratio
- The &P command controls the ratio of the off-hook (make) to on-hook
(break) interval used by the modem when it pulse dials. &P0 selects a
39%/61% make/break ratio for use in the U.S. &P1 selects a 33%/67%
make/break ratio for use in the United Kingdom and Hong Kong. The &P command
is NOT allowed in some countries.
- Monochrome Display Adapter. Early IBM Video display board designed for use
with IBM monochrome text standard.
- Musical Instrument Digital Interface. A standard which allows for the
exchange of data between two music synthesizers or a synthesizer and a computer.
Sound data may be communicated from the synthesizer to the computer and stored
as a MIDI file. Or, a MIDI file can be transmitted to the synthesizer for
- Microcom Networking Protocol. A series of data communications protocols
developed by Microcom for full-duplex, error-free communications.
- Modulation Handshake
- Also referred to as Automode Enable and is controlled by the ATN command.
This determines whether or not the modem must connect at a particular speed, or
allow connection at any speed supported by both modems.
- A UART on the MIDI port which allows MIDI interface to transmit and receive
at 32.5K baud (see Appendix E for more information).
- (Motion Pictures Expert Group). A type of data compression storage and
playback of video and audio data.
- An abbreviation for megabits per second. A measurement of the
transmission speed of data measured in 1,048,576 bits per second.
- Multiple Frequency Monitor
- Monitor capable of displaying video signals over a wide range of horizontal
scan frequencies. This may include a horizontal capture range from 5.5KHz to
35KHz or wider. Examples of monitors in this class are the NEC MultiSync and the
Sony Multiscan. The Multiscan has a wide horizontal scan capture range which
enables it to display monochrome signals.
- Negotiation Fallback
- Controlled by S-Register 36 as part of the V.42 protocol. Setting this
register indicates what action to take when a desired connection cannot be made
(e.g., hang-up, direct mode connect, normal mode connect).
- network adapter card
- A board in your PC that has one or more ports for connection to a
- Network topology
- The arrangement of nodes usually forming a star, ring, tree, or bus
- Any device including servers and workstations connected to a network; also
the point where devices are connected.
- Non-Volatile RAM
- Also NVRAM. Random access memory whose data is retained when power is
turned off. This is especially useful for modems to store user-defined default
configuration settings and frequently used telephone numbers. This information
would be loaded into modem RAM at power-up.
- On-Line State
- Same as data mode. To transmit or receive data, the modem must be in the
on-line state. When placing a call, the modem is put on-line with the dial
- A collection of bits comprising data and control information formatted for
transmission from one node to another.
- The range of colors from which you can select the actual colors that the
video adapter will display simultaneously.
- parallel port
- One of several kinds of connectors found on the back of computers used
to connect peripherals. Peripherals that connect to parallel ports include
printers, Zip drives, tape drives and CD-ROM drives.
- Private Branch Exchange. A telephone switch at a customer site.
- A sound's tone, usually determined by the sound's frequency
- A single dot on the CRT display. This word is derived from the words
'picture' and 'element'.
- Plug and Play
- An industry-wide standard for add-on hardware which indicates that it
will configure itself, thus eliminating the need to set jumpers, and
making installation of the product quick and easy.
- A standardized set of rules that specify the format, timing, sequencing,
and/or error checking for data transmissions.
- Pulse Dialing
- Also referred to as rotary dialing, i.e., dialing with the older-style
rotary dial wheel. The dial modifier ATDP sets the modem to pulse dialing, which
is the default method as opposed to tone dialing (push-button touch-tone) which
is enabled with ATDT. All telephone exchanges will accept older-style pulse
dialing and most exchanges will accept modern tone-dialing. Tone dialing is
faster and more reliable since mechanical relays and their inherent failure
mechanisms are avoided.
- RAM Digital to Analog Converter.
- Refresh Rate
- Also called Vertical Scan Rate, the speed at which the screen is repainted.
Typically, color displays must be refreshed at 60 times per second. Usually, the
faster the refresh rate, the less flicker a monitor has (normally defined in
- Register Level Compatibility
- Complete compatibility to the hardware level.
- Used to extend the topology, allowing two or more cable segments to be
joined. In a 10Base-T network, the repeater provides the central connection
point where the gathering of statistics and network management functions take
- Result Code
- A response sent by the modem after executing a command. The response
reports the modem's status or the progress of a call and can take the form of
either digits (numeric) or words (verbose). Issuing a V1 command enables word
responses. A V0 (V-zero) command enables numeric responses. The Q1 command
disables their use entirely. Example: "OK" (word), or 0 (numeric)
indicates that the modem successfully executed a command.
- An adjustment process performed when one of the modems detects signal
distortion or line noise which threaten data integrity.
- RGB Monitor
- Red/Green/Blue. A CGA compatible monitor limited to a 15.750KHz horizontal
- Ring Topology
- A network topology in which nodes are connected in a closed loop; no
terminators are required because there are no unconnected ends.
- RJ-45 connector
- A connector utilized in 10BaseT and 100BaseTX networks with UTP cabling.
- Request to Send/Clear to Send. RTS and CTS are two control signal lines
between the modem (DCE) and terminal (DTE) which allow the terminal to control
the flow of information. See also flow control.
- A measurement of sound taken during a certain duration. In digital
recording, sampling means recording voltages which make a sound as a sequence of
numerical values representing the sound's amplitude.
- Scan Rate
- The frequency in Hertz (Hz) at which the monitor is scanned horizontally.
Generally, the higher the scan rate, the higher the resolution.
- serial port
- One of several kinds of connectors found on the back of computers used
to connect peripherals. Peripherals that connect to serial ports include
external modems, ISDN terminal adapters and mice.
- A computer that provides shared resources, such as files and printers, to
- Sleep Inactivity Timer
- Determines the length of time the modem operates in normal mode with no
activity before entering low-power "sleep" mode.
- software configurable
- The ability of an add-on product to be configured by its software, thus
eliminating the need to set jumpers, and making installation of the
product quick and easy.
- Sound File
- Any file which holds sound data. Examples: files with .MID file name
extensions are compatible with the MIDI standard (see above); a file with a .WAV
file name extension is a standard Microsoft file format for storing waveform
audio data. See Waveform and wave file.
- Split-Speed Direction
- Determines which direction (transmit or receive) has the 75bps channel and
which has the 1200bps channel.
- Standard AT-Command
- The basic AT command set, originated by Hayes Microcomputer Products, Inc.
- Star Topology
- A network topology in which nodes are connected to a common device such as
hub or concentrator.
- Synchronous Communications
- A method of transmission in which data bits are sent continuously at the
same rate under the control of a fixed frequency clock signal.
- A T-shaped device with two female and one male BNC connectors.
- 50-ohm coaxial plug used to attach to one end of a BNC T-connector when
the associated station is first or last in the group.
- thin coaxial cable
- A networking cable with BNC terminators used on 10Base2 networks.
- How the ear identifies and classifies sound. Example: the timbre of the
same note played by two different instruments (flute and tuba) will not be the
- Touch-Tone Dialing
- Push-button tone dialing as used on contemporary phone sets. The dial
modifier ATDT sets the modem to "tone" mode. Tone dialing is faster
and more reliable than older-style pulse dialing.
- The physical layout of a network. The principal LAN topologies are bus,
ring, and star.
- An AUI (Attachment Unit Interface) device for receiving and transmitting
data that often provides collision detection as well.
- Trellis Coding
- A method of modulation which targets specific modulation points. Signals
falling outside of these points are treated as line noise, thus ensuring greater
noise immunity over a given line. QAM (Quadrature Amplitude Modulation)
functions similarly, but has a broader tolerance and results in lesser noise
immunity than trellis coding.
- Terminate and Stay Resident. A program that remains in memory after it has
- Transistor-Transistor Logic; a fast, reasonable-cost type of integrated
circuit used in some monitors.
- TTL Monitor
- Video and synchronization signals (all digital) are on separate lines and
have TTL compatible voltage levels
- Twisted-Pair cable
- A wiring scheme with one or more pairs of 18 to 24- gauge copper strands.
- UTP cable
- An abbreviation for unshielded twisted-pair cable. A networking cable
with RJ-45 connectors used on 10BaseT and 100BaseTX networks.
- Video Electronics Standards Association.
- (Video Graphics Array) Analog graphics standard introduced with the IBM
PS/2 series. Backwards compatible with EGA at the BIOS level, but provides
higher resolutions. Supports a maximum resolution of 640 x 480 pixels in 16
colors out of a palette of 262,144 colors.
- Voice Annotation
- Embedding of a voice message into a document for later playback.
- A modem standard established by the ITU which assures that 56K modems
that comply with the standard will be able to communicate with one
another regardless of the manufacturer of the modem.
- (Wide-Area Network) A network which uses common carrier-provided lines;
contrast with LAN.
- Wave File
- A standard Microsoft file format for storing waveform audio data.
- A graph showing the amplitude of a sound over a particular interval of
time. Any portion of that interval is a sample.
- XON and XOFF are the names of two different flow control characters. See
also flow control.