Networking Glossary

Networking Glossary of Terms

#A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

10/100 Dual Speed
Ethernet supported network devices based on 10 Mbps and Fast Ethernet 100 Mbps technologies.

IEEE 802.3 standard for a twisted-pair Ethernet network. 10 Mbps transmission rate over baseband using unshielded, twisted-pair cable.

IEEE standard for a 100 Mbps baseband Ethernet over twisted-pair wire.

54g+ (Xpress)
54g+ is a technology that utilizes standards based on framebursting to achieve higher throughput. With 54g+ enabled, aggregate throughput (the sum of the individual throughput speeds of each client on the network) can improve by up to 25% in 802.11g only networks and up to 75% in mixed networks comprised of 802.11g and 802.11b equipment.

54g Mode
If you are having difficulty connecting to an 802.11b wireless only router, try switching your 5430 to 802.11b only mode and do the same with your wireless router. This will ensure you are connecting to 802.11b devices only. Set the mode to 54g Auto for the widest compatibility. Set the mode to 54g Performance for the fastest performance among 54g certified equipment.

54g Protection
The 802.11g standards provide a protection method so 802.11g and 802.11b devices can co-exist in the same network without “speaking” at the same time. Do not disable 54g Protection if there is a possibility that a 802.11b device may need to use your wireless network. In Auto Mode, the wireless device will use RTS/CTS to improve 802.11g performance in mixed 802.11g/802.11b networks. Turn protection off to maximize 802.11g throughput under most conditions.

64 and 128 bit encryption
64 and 128-bit encryption (also called domestic-, U.S.-grade, or strong encryption) is technology that encodes information so it cannot be read without decoding.

This is an IEEE standard that specifies the Logical Link Control (LLC) that is common to all 802 series LANs.

IEEE standard that specifies a carrier sense medium access control and physical layer specifications for wired LANs.

IEEE standard that specifies a token-passing bus access method and physical layer specifications for wired LANs.

IEEE standard that specifies a token-passing ring access method and physical layer specifications for wired LANs.

IEEE standard that specifies security and privacy access methods for both wired and wireless LANs.

IEEE standard that specifies medium access and physical layer specifications for 1 Mbps and 2 Mbps wireless connectivity between fixed, portable, and moving stations within a local area.

The IEEE (Institute of Electrical and Electronic Engineers) released the 802.11 specifications in June 1999. The initial specification, known as 802.11, used the 2.4 GHz frequency and supported a maximum data rate of 1 to 2 Mbps. In late 1999, two new addenda were released. The 802.11b specification increased the performance to 11 Mbps in the 2.4 GHz range while the 802.11a specification utilized the 5 GHz range and supported up to 54 Mbps.

Unfortunately, the two new specifications were incompatible because they used different frequencies. This means that 802.11a network interface cards (NICs) and access points cannot communicate with 802.11b NICs and access points. This incompatibility forced the creation of the new draft standard known as 802.11g. 802.11g supports up to 54 Mbps and in interoperable with 802.11b products on the market today.

802.11a operates in the 5-6 GHz range with data rates commonly in the 6 Mbps, 12 Mbps, or 24 Mbps range. Because 802.11a uses the orthogonal frequency division multiplexing (OFDM) standard, data transfer rates can be as high as 54 Mbps. OFDM breaks up fast serial information signals into several slower sub-signals that are transferred at the same time via different frequencies, providing more resistance to radio frequency interference. the 802.11a specification is also known as Wi-Fi5, and though regionally deployed, it is not a global standard like 802.11b.

Ratified by the IEEE (Institute of Electrical and Electronic Engineers) in July 1999, the 802.11b standard (also known as Wi-Fi) operates in the 2.4 GHz range with up to 11 Mbps data rates and is backward compatible with the 802.11 standard. 802.11b uses a technology known as complementary code keying (CCK) modulation, which allows for higher data rates with less chance of multi-path propagation interference (duplicate signals bouncing off walls).

802.11g operates in the 2.4 GHz range with data rates as high as 125 Mbps over a limited distance. It is also backward compatible with 802.11b and will work with both 11 and 22 Mbps wireless networking products. 802.11g offers the best features of both 802.11a and 802.11b and as of June 2003, the IEEE 802.11g standard was officially approved.

802.11n is the latest standard under development by the IEEE (Institute of Electrical and Electronic Engineers), for wireless data communications, aimed at boosting data throughput to a theoretical 540 Mbps, or 10 times faster than the 802.11g standard. Various products have been delivered based on earlier draft versions, or using components of earlier versions that were expected to become part of the final standard. The current Draft 2 version was closed by vote of the 802.11n Working Group in March of 2007 and is expected to closely resemble the final standard that is expect to be published in September 2008.


Adaptive Speed Leveling (ASL)
A Courier( feature, first used by V.32 bis and V.32 terbo modems in November 1990, that detect interference on a line or improved line conditions and shift accordingly. This feature allows the send and receive channels of a modem connection to adapt independently to varying line conditions. Each channel shifts down in speed when interference is detected and back upward again when line conditions improve without affecting the performance of the other channel. The modems at both ends of the connection adapt independently, each detecting and adjusting to line conditions. ASL keeps the modems online, always operating at the highest possible speed, and constantly ensuring data integrity.

Adhoc Mode
Sometimes referred to as head-to-head or peer-to-peer, adhoc mode functions without the aid of an access point (AP). Adhoc is an 802.11 networking configuration whereby wired or wireless devices communicate with each other, often used with gaming consoles for the purposes of LAN Party gaming.

Adaptive Differential Pulse Coded Modulation. This is used in voice compression algorithms.

Acoustic Echo Cancellation. This is used in Speakerphone technology.

Automatic Gain Control. This is used in Speakerphone technology.

Analog Interface Circuit. Used on all modems.

One of many sound file formats for the Macintosh computer.

Anonymous FTP
A manner of logging into an FTP site as a public user. Many FTP sites will allow anonymous logins to access some files.

American National Standards Institute - Generic body for U.S. Standards.

Answer Mode
A state in which the modem transmits at the predefined high frequency of the communications channel and receives at the low frequency. The transmit/receive frequencies are the reverse of the calling modem which is in Originate mode.

Automatic Repeat Request. A general term for error control protocols which feature error detection and automatic retransmission of defective blocks of data. See HST(, MNP, and V.42.

American Standard Code for Information Interchange. The format used for standard unformatted text. A 7bit binary code (0's, 1's) used to represent letters, numbers, and special characters such as $, !, and /. Supported by almost every computer and terminal manufacturer.

Applications Specific Integrated Circuit. Used on all USRobotics modems.

Asymmetrical Modulation
A duplex transmission technique which splits the communications channel into one high speed channel and one slower channel. During a call under asymmetrical modulation, the modem with the greatest amount of data to transmit is allocated the high speed channel. The modem with less data is allocated the slow, or back channel (450 bits per second (bps)). The modems dynamically reverse the channels during a call if the volume of data transfer changes.

Asynchronous Transmission
Transmission in which the length of time between transmitted characters may vary. Because the time lapses between transmitted characters are not uniform, the receiving modem must be signaled as to when the data bits of a character begin and when they end. The addition of Start and Stop bits to each character serves this purpose. Compare to Synchronous Transmission.

Asynchronous Transfer Mode. A network technology based on transferring data in cells or packets of a fixed size. The cell used with ATM is relatively small compared to units used with older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the lines. Current implementations of ATM support data transfer rates of from 25 to 622 Mbps (megabits per second).

A sound file format for UNIX systems.

Auto Answer
A feature in modems enabling them to answer incoming calls over the phone lines without the use of a telephone receiver.

Auto Dial
A feature in modems enabling them to dial phone numbers over the phone system without the use of a telephone transmitter.

Analog Wide Area Network

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Baud Rate
The number of discrete signal events per second occurring on a communications channel. The communications carrier frequency. Due to advanced coding methods, each signal can carry more than one bit. At 300 baud, approximately 300 bits are transmitted per second. For speeds higher than 2400, baud rate and bit rate are no longer equivalent. Although not technically accurate, baud rate is commonly used to mean bit rate (bps). In communications software, baud rate refers to the computer’s serial port rate. See UART.

Electronic Bulletin Board System

Beacon Interval
A beacon is a packet of information that is sent from a connected device to all other devices where it announces its availability and readiness. A beacon interval is a period of time (sent with the beacon) before sending the beacon again. The beacon interval may be adjusted in milliseconds (ms).

Bell 103
A standard for modem data communication at 300 bps. See V.21.

Bell 212A
A standard for modem data communications at 1200 bps. See V.22.

Beta Test
Second stage testing performed by dependable customers who volunteer to use a product and report any problems, before the product is actually released.

Binary Digit
A 0 or 1, reflecting the use of a binary numbering system (only two digits). Used because the computer recognizes either of two states, OFF or ON. Shortened form of binary digit is bit.

Binary Synchronous Control. An earlier protocol developed by IBM for software applications and communicating devices operating in synchronous environments. The protocol defines operations at the link level of communications, for example, the format of data frames exchanged between modems over a phone line. See Protocol, HDLC, SDLC.

Bit Rate
The number of binary digits, or bits, transmitted per second (bps). Communications channels using telephone channel modems are established at set bit rates, commonly 300, 1200, 2400, 4800, 9600, and 14400.

Bits per Second
The bits (binary digits) per second rate. A 14,400 Sportster(, for example, is capable of transmitting 14,400 bits per second to another modem capable of at least 14,400 bps.

Data communications software made by CRG, mainly for file transfer and the name of the file transfer protocol.

Bluetooth is a computing and telecommunications industry specification that describes how mobile phones, computers, and personal digital assistants (PDAs) - such as a PalmPilot - can easily interconnect with each other. This technology is used with home and business phones as well as computers via a wireless connection.

Bits Per Second.

Basic Rate Interface - 2B+D ISDN connection

A memory area used as temporary storage during input and output operations. An example is the modem's command buffer. Another is the Transmit Data flow control buffer used for flow control and to store copies of transmitted frames until they are positively acknowledged by the receiving modem.

A group of binary digits stored and operated upon as a unit. A byte may have a coded value equal to a character in the ASCII code (letters, numbers), or have some other value meaningful to the computer. In user documentation, the term usually refers to 8-bit units or characters. 1 kilobyte (K) is equal to 1,024 bytes or characters; 64K indicates 65,536 bytes or characters.

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Call Link
Software based phone system

Formerly, an international organization that defined standards for telegraphic and telephone equipment. It has been incorporated into its parent organization, the International Telecommunication Union (ITU). Telecommunication standards are now covered under Telecommunications Standards Sector (TSS). ITU-T replaces CCITT. For example, the Bell 212A standard for 1200 bps communication in North America was referred to as CCITT V.22. It is now referred to as ITU-T V.22.

A representation, coded in binary digits, of a letter, number, or other symbol.

Characters Per Second
A data transfer rate generally estimated from the bit rate and the character length. For example, at 2400 bps, 8-bit characters with Start and Stop bits (for a total of ten bits per character) will be transmitted at a rate of approximately 240 characters per second (cps). Some protocols, such as USR-HST and MNP, employ advanced techniques such as longer transmission frames and data compression to increase cps.

Class 1/EIA-578
An American standard used between facsimile application programs and facsimile modems for sending and receiving Class 1 faxes.

Class 2.0/EIA-592
An American standard used between facsimile application programs and facsimile modems for sending and receiving Class 2.0 faxes.

A computer that connects to a server which exchanges information.

Client Mode
Sometimes referred to as Infrastructure Mode, Client Mode is most commonly used when connecting a gaming console to the Internet through the use of a wireless gaming adapter and a wireless router or access point. Client Mode may be used as an Ethernet bridge to connect any Ethernet device such as a computer, network printer, or digital video recorder (DVR) to a wireless network.

Crossover Cable
This refers to an Ethernet cable using RJ-45 connectors, where one end of the cable is wired so that the Receive signal pins on one connector are connected to the Transmit signal pins on the other connector. A Crossover Cable may be used to connect two 10BaseT or 100BaseT network cards, basically making a network of two computers, for example.

Compressed Serial Line Internet Protocol- A SLIP protocol that compresses the amount of information in the packet header. Also see SLIP.

Cyclic Redundancy Checking (CRC)
An error-detection technique consisting of a cyclic algorithm performed on each block or frame of data by both sending and receiving modems. The sending modem inserts the results of its computation in each data block in the form of a CRC code. The receiving modem compares its results with the received CRC code and responds with either a positive or negative acknowledgment. In the ARQ protocol implemented in USRobotics high speed modems, the receiving modem accepts no more data until a defective block is received correctly.

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Data Communications
A type of communications in which computers and terminals are able to exchange data over an electronic medium.

Data Compression (Computer)
Storage of programs, files, and data on a hard drive or other storage device in compressed format so as to require less storage space. Can be done manually using a compression utility such as PKZIP, or can be done automatically using a utility such as Stacker or DoubleSpace.

Data Compression (Modem)
When the transmitting modem detects redundant units of data, it recodes them into shorter units of fewer bits. The receiving modem then decompresses the redundant data units before passing them to the receiving computer.

Data Communication (or Circuit-Terminating) Equipment. In this manual, the term applies to dial-up modems that establish and control the data link via the telephone network.

Dedicated Line
A user-installed telephone line used to connect a specified number of computers or terminals within a limited area, for example, one building. The line is a cable rather than a public-access telephone line. The communications channel may also be referred to as nonswitched because calls do not go through telephone company switching equipment.

Dynamic Host Configuration Protocol (DHCP)
A Dynamic Host Configuration Protocol is a protocol used for assigning dynamic IP addresses to a device on a network. DHCP simplifies network administration because the software keeps a log of IP addresses and in doing so, allows an administrator to add computers to a network without the hassle of manually assigning a unique IP address each time.

Digital Signals
Discrete, uniform signals. In this manual, the term refers to the binary digits 0 and 1.

A subsection of the internet of an IP address which is most commonly used to refer to a group of computers whose hostnames share a common suffix: the domain name. The primary domains are: .COM, .ORG, .NET, .MIL.

Domain name
The information located to the right of the @ in an address, this is also referred to as DNS. e.g. In this case is the domain

Domain Name Server- A system used to translate hostnames like USR.COM to a numeric Internet address. The DNS will also provide naming for clients as well as hosts.

Digital Signal Processor. Frequently called the “data pump.” A chip in the modem’s circuitry that handles all of the actual work of sending and receiving data.

DTIM Interval
The DTIM Interval sets the Wake-up interval for clients in power-saving mode.

Indicates a communications channel capable of carrying signals in both directions. See Half Duplex, Full Duplex.

Dynamic IP Address
A Dynamic IP Address is a number or protocol used to connect to a network. As the name implies, dynamic addressing uses a different IP address each time a connection is verified via the Internet.

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(Electronically Eraseable Programmable Read Only Memory) replaced ROM in our new models of modems. This is permanent memory too. The only way that a user can write to this memory is through an executable program that erases the code written there and new code files contained in the program are written to the EEPROM. (Also known as EPROM, which is the way it is listed under ATI7) This makes flashing a modem for an upgrade or update possible.

EIA Standards Committee
Electronic Industries Association, which defines electronic standards in the U.S.

Error Control
Various techniques which check the reliability of characters (parity) or blocks of data. V.42, MNP and HST error control protocols use error detection (CRC) and retransmission of frames in error (ARQ). Error control is a required component of data compression.

Error Detection
The process of determining whether errors have been introduced to transmitted data. Although some people use the terms “error detection” and error correction” interchangeably, it is important to note that the modem does not perform error correction. If errors are detected, the receiving modem sends a request for the sending modem to start over again where the errors where first encountered. Formerly parity was used as a method of error detection, but as the speed increased and the amount of data increased, this was not effective.

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A system set up to monitor and block certain types of traffic between a network or networks and the internet. This is mainly set up for security reasons, to prohibit unauthorized access of confidential information.

Flash ROM
Read Only Memory that can be erased and reprogrammed with software. Most USRobotics Courier modems can be updated or upgraded using a program downloadable from the USRobotics BBS when available.

Flow Control
A feature that compensates for differences in the flow of data input to and output from a modem or other device. Necessary to keep a modem from sending data faster than a computer can handle it, to prevent overflow and data loss.

Fragmentation Threshold
This threshold is used to fragment packets which help improve performance in the presence of RF interference.

File Transfer Protocol- A protocol used for sending files from one computer to another.

Full Duplex
Signal flow in both directions at the same time. In microcomputer communications, may refer to the suppression of the online Local Echo. Telephones operate in full duplex, as they are capable of sending and receiving signals at the same time. See also Simplex, Duplex, Half Duplex.

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A system by which two incompatible networks or applications can communicate with each other.

Graphical User Interface- An interface that is accessed by icons and other graphical images. Windows and Macintosh systems use a GUI.

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Half Duplex
Signal flow in both directions, but only one way at a time. In microcomputer communications, may refer to activation of the online Local Echo, which causes the modem to send a copy of the transmitted data to the screen of the sending computer. Walkie talkies use Half Duplex transmission, because they cannot send and receive signals at the same time.

The part of a data packet which contains the source and destination address of that data packet. A header is like an envelope for a letter.

High Level Data Link Control. A standard protocol developed by the International Standards Organization for software applications and communicating devices operating in synchronous environments. The protocol defines operations at the link level of communications, for example, the format of data frames exchanged between modems over a phone line. See Bisync, Protocol, SDLC.

A unique name by which a computer is known on a network. The hostname is also used to identify it in electronic mail or other forms of electronic information interchange over a network or internet.

HST(High Speed Technology)
USRobotics' proprietary signaling scheme, design and error control protocol for high-speed modems. HST incorporates trellis-coded modulation, for greater immunity from variable phone line conditions, and asymmetrical modulation for more efficient use of the phone channel at speeds of 4800 bps and above. HST also incorporates MNP-compatible error control procedures adapted to asymmetrical modulation.

Hyper Text Markup Language- The language or format in which Web pages are written.

Hyper Text Transport Protocol- The system used to request HTML documents from the World Wide Web.

A hub is a place where data arrives from one or more directions and is forwarded out in one or more other directions. A hub - sometimes called a switch - is typically defined as the location where data comes together. A switch (if distinguished from a hub) is a networking tool designed to determine how and where data is forwarded from the place where data comes together.

Hertz, a frequency measurement unit used internationally to indicate one cycle per second.

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Infrastructure Mode
An 802.11 networking framework in which devices communicate with each other by first going through an Access Point (AP). In infrastructure mode, wireless devices can communicate with each other or can communicate with a wired network. Generally, a majority of corporate wireless LANs operate in infrastructure mode because they require access to the wired LAN in order to use services such as file servers or printers.

The physical and logical arrangement supporting the attachment of any device to a connector or to another device.

Internet Connection Sharing (ICS)
ICS is a method for connecting multiple computers in a LAN to the Internet through a single connection and a single IP address. ICS follows a client/server model. To set up ICS, one computer must be chosen as the "server." This computer must support two network interfaces, one directly connected to the Internet and the other connected to the remainder of the LAN. In a traditional home dial-up network, for example, the server computer is directly connected to the modem.

Intranet is a TCP/IP network inside a company that links that company to the Internet. Most Intranets are only accessible from within the location or company that runs that Intranet.

IP Address
All computers on the Internet use an IP address for identification purposes. The format of this address is three dots and four groups of numbers. There is a network number, host number, and a subnet address. i.e. 1.22.333.44

Internetwork Packet eXchange- A protocol used to link Local Area Networks to each other with a router device.

Internet Relay Chat- The live chat area of the internet.

Integrated Switched Digital Network- A digital telephone system which provides noise free high speed communications. The service is a custom service that must be installed by the phone company. You will need a Terminal Adapter, a telephone provider which supports ISDN, and a service provider. Usually telephone exchange carriers use digital lines to communicate with one another, but it is possible to have one of these digital lines installed directly into your home or office. Results in higher speed, fewer errors, and allows for separate lines and communications channels. No analog signal is modulated (no modem), but usually a Terminal Adapter is required because digital signals differ.

Internet Service Provider- A company which provides access to the Internet whether it is a personal dial-up account or a cooperate networked connection. Most ISPs will provide extra services include help with design, creation and administration Web sites, and intranet support for companies.

International Telecommunication Union-Telecommunication sector. Formerly referred to as CCITT. An international organization that defines standards for telegraphic and telephone equipment. For example, the Bell 212A standard for 1200 bps communication in North America is observed internationally as ITU-T V.22. For 2400 bps communication, most U.S. manufacturers observe V.22 bis.

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Local Area Network- A computer network located in one or more buildings.

LAN Party
A LAN Party is a group of individuals with two or more gaming consoles, TVs, and games, in the same building or house, sharing a router or access point to communicate in head-to-head, peer-to-peer, or Adhoc Mode.

Link Access Procedure for Modems, an error control protocol incorporated in ITU-T Recommendation V.42. Like the MNP and HST protocols, LAPM uses cyclic redundancy checking (CRC) and retransmission of corrupted data (ARQ) to ensure data reliability.

Leased Line
A phone line, leased from the phone company, set up specifically as a direct connection between two fixed locations. There is no dial tone on these lines. Only Courier modems support leased lines.

A term used to describe products that are

A reference point from one site or location which will point you to another location for that information.

Listserv an automatic email server. This server processes electronic mail requests for addition to or deletion from mailing lists. Some listservs provide facilities such as retrieving files from archives and a database search.

Local Echo
A modem feature that enables the modem to send copies of keyboard commands and transmitted data to the screen. When the modem is in Command mode (not online to another system) the local echo is invoked through the ATE1 command. The command causes the modem to display your typed commands. When the modem is online to another system, the local echo is invoked through the ATF0 command. This command causes the modem to display the data it transmits to the remote system.

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MAC Address
The MAC (Media Access Control) address is your computer's hardware number on your local area network (LAN). When connected to the Internet from your computer, a correspondence table relates your IP address to your computer's physical (MAC) address on the LAN.

Multipurpose Internet Mail Extension- A file format that will allow you to post non-text data in a mail message. Graphic files, video, audio, and executables file can be sent via email using this manner.

Microcom Networking Protocol, an asynchronous error control protocol developed by Microcom, Inc. and now in the public domain. The protocol ensures error-free transmission through error detection (CRC) and retransmission of errored frames. USRobotics modems use MNP Levels 4 and Level 5 data compression. MNP Levels 4 have been incorporated into ITU-T Recommendation V.42. Compare HST.

The word modem is actually an acronym for modulate and demodulate. A modem is a serial device that modulates the computer’s digital data into analog signals compatible with the Public Switched Telephone Network (PSTN) to communicate over an analog telephone line and demodulates analog signals into digital data to communicate with the computer.

Multi-User Dungeon- This goes by many other names as well. A format in which games are played over the internet. This is usually a text based game, but it can be used for conferencing and educational purposes. They are accessed via telnet or other specialized client programs.

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Network Address Translation (NAT)
Sometimes referred to as IP Masquerading, a NAT allows the local network to utilize private IP addresses. As information travels to the public IP address, the gateway translates the traffic from the public IP address to the private IP address for the computer that requested the information.

NetBIOS (Network Basic Input/Output System) is a program that allows applications on different computers to communicate within a local area network (LAN). NetBEUI does not support the routing of messages to other networks. Its interface must be adapted to other protocols such as Internetwork Packet Exchange or TCP/IP.


Nonvolatile Memory (NVRAM)
User-programmable random access memory whose data is retained when modem power is turned off. Used in Courier modems to store a user-defined default configuration loaded into random access memory (RAM) at power on.

A company that develops software to allow PC’s to link together using today’s networking hardware.

(Non-volatile Random Access Memory) is user-programmable random access memory whose data is retained when modem power is turned off. Used in modems to store a user-defined configuration which can be loaded into RAM at power on.

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Original Equipment Manufacturer.

Online Gaming
Online gaming is just as it sounds: A gaming console is configured wired or wirelessly through a router or access point for the purposes of gaming online through the Internet. This allows the end-user to play anyone around the world.

Online Fallback
A feature that allows high speed error-control modems to monitor line quality and fall back to the next lower speed if line quality degrades. The modems fall forward as line quality improves.

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A unit of data which is sent through a network. A packet will consist of many layers of information. Each layer of information will address an aspect of that data packet, from the “where” and “who” information to the type of information that is being sent.

Based on the electric-field transmission medium, Personal Area Network (PAN) allows individuals to exchange data with a simple touch or grasp, such as a handshake. For example, two people each wearing business card-size transmitters and receivers conceivably could exchange information by shaking hands. A PAN user is equipped with a receiver and a transmitter, which constantly sends infinitesimal data-carrying currents -- in the 0.1-1 MHz band -- through the body and picks up currents when in very close range with another device or individual carrying a transmitter.

Parallel Transmission
The transfer of data characters using parallel electrical paths for each bit of the character, for example, 8 paths for 8-bit characters. Data is stored in computers in parallel form, but may be converted to serial form for certain operations. See Serial Transmission.

An error-detection method that checks the validity of a transmitted character. Character checking has been surpassed by more reliable and efficient forms of block-checking, including Xmodem-type protocols and the ARQ protocol implemented in Courier modems. The same type of parity must be used by two communicating computers, or both may omit parity. When parity is used, a parity bit is added to each transmitted character. The bit's value is 0 or 1, to make the total number of 1's in the character even or odd, depending on which type of parity is used.

Personal Computer. Generally refers to an IBM compatible computer (386, 486, Pentium, etc.).

peer-to-peer (P2P)
Peer-to-peer is a type of Internet network allowing a group of computer users with the same networking program to connect with each other for the purposes of directly accessing files from one another's hard drives.

Phone Line Networking
Phone line networking allows all the components of a home network to interact over the home's existing telephone wiring without disturbing the existing voice or fax services.

Post Office Protocol- A protocol designed to read electronic mail from a server. There are three versions: POP, POP2, and POP3 which are commonly used on today’s computers.

Power Line Networking
Power line networking allows all the components of a home network to interact over the home's existing electrical outlets without disturbing the existing voice or fax services.

Point to Point Protocol- An internet protocol used to send packets of internet information over serial points to point links.

Plug-ins are software programs that extend the capabilities of your Web browser. They allow you to play audio, video, and view 3D graphics through your browser.

Preamble Type
Preambles are a sequence of binary bits that help the receivers synchronize and ready for receipt of a data transmission. Some older wireless systems like 802.11b implementation use shorter preambles. If you are having difficulty connecting to an older 802.11b device, try using a short preamble. You can select short preamble on if the 54g mode is set to 802.11b Only in the 54g Mode field.

Exclusively owned, made, and sold by one holding a trademark or patent. HST is a proprietary protocol of USRobotics.

A system of rules and procedures governing communications between two or more devices. Protocols vary, but communicating devices must follow the same protocol in order to exchange data. The format of the data, readiness to receive or send, error detection and error correction are some of the operations that may be defined in protocols.

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A waiting line. For example, in a print queue, if a document is sent by person A, then by person B, then by person C, the jobs to be printed would be stored in a queue, job A would be printed, then job B, then job C.

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Random Access Memory. Memory that is available for use when the modem is turned on, but that clears of all information when the power is turned off. The modem's RAM holds the current operational settings, a flow control buffer, and a command buffer.

Remote Access
A feature that allows a remotely-located user to view the Courier's configuration screens and change the Courier's configuration. Password protection is available.

Technical name for a standard phone cable used by telephones and modems. One RJ11 cable is supplied with each of our desktop modem products.

RTS Threshold (Request to Send Threshold)
The RTS threshold determines the packet size of a transmission and, through the use of an access point, helps control traffic flow.

(Random Access Memory) is available for use when the modem is turned on, but clears of all information when the power is turned off. User may write to this memory. The modem’s RAM holds the current settings.

(Read Only Memory) is permanent memory and the user may not write to this memory. The modem’s factory settings are stored in ROM and can be read (loaded) into RAM as an operational configuration or current settings.

A device which passes information from one network to another.

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Serial Port
A nine- or 25- pin male port found on the back of a computer, which, via an RS-232C cable, connects to the serial port on a modem. Most computers have two serial ports, COM1 and COM2. A computer’s serial ports are run by UART chips, which come in different speeds. See UART.

Serial Transmission
The transfer of data characters one bit at a time, sequentially, using a single electrical path. See Parallel Transmission.

Signal Ground

Software that is offered free to try. If the software is used beyond the trial period, it will need to be registered with the company or individual that produced it. There is usually a fee for the registration of the software. Most shareware applications are posted on the Internet, on-line services, and Bulletin Boards.

Simplex (Transmission)
Indicates a comunications system capable of transmitting a signal in only one direction, for example, an FM radio channel.

Subscriber Line Interface Circuit - A standard RJ11 telephone jack

Serial Line Internet Protocol- Is used to connect a remote computer to the Internet using a modem.

Stateful Packet Inspection (SPI)
Stateful Packet Inspection (SPI) is a firewall monitoring system that verifies the destination of inbound and outbound packet requests. Similar to Network Address Translation (NAT), SPI takes the architecture of router firewall protection further by examining the structure or layer of inbound and outbound packets. This allows for a broader filtering scope to include the more traditional administrator defined rules (as in static packet filtering) but also the information from prior packets that have passed through the firewall.

USRobotics line of desktop modems.

Start/Stop Bits
The signaling bits attached to a character before the character is transmitted during Asynchronous Transmission.

Static IP Address
A Static IP Address is a number assigned to a computer by an Internet Service Provider (ISP) to be its permanent address on the Internet. Static IP Addresses allow for Web hosting locally at home or the office and are used for remote access over the Internet. Static IP Addresses do not work with analog dial-up connections.

Straight-through Cables
Straight-through cables are used for connecting computers to a hub. In a straight-through cable, wires 1, 2, 3, and 6 at one end of the cable are also wires 1, 2, 3, and 6 at the other end. In a crossed cable, the order of the wires change from one end to the other: wire 1 becomes 3, and 2 becomes 6.

Synchronous Data Link Control. A protocol developed by IBM for software applications and communicating devices operating in IBM's Systems Network Architecture (SNA). The protocol defines operations at the link level of communications, for example, the format of data frames exchanged between modems over a phone line. See Bisync, Protocol, HDLC.

Simple Mail Transfer Protocol- One of the protocols under the TCP/IP group of protocols used to transfer electronic mail between computers.

A switch is a network device that selects a path or circuit for sending a unit of data to its next destination. A switch may also include the function of the router, however, a switch is more simplistic in function.

Synchronous Transmission
A form of transmission in which blocks of data are sent at strictly timed intervals. Because the timing is uniform, no Start or Stop bits are required. Compare Asynchronous Transmission. Some mainframes only support synchronous communications unless their owners have installed a synchronous adapter and appropriate software.

A SYStems OPerator. A person who runs a bulletin board (BBS).

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Terminal Adapter - Used in ISDN connections

Transmission Control Protocol / Internet Protocol- A protocol that allows you to access services on the internet such as Telenet, FTP, email and other services.

A TCP/IP application that allows you to connect to other host systems on the internet. Some Bulletin boards can be access via Telnet.

A device whose keyboard and display are used for sending and receiving data over a communications link. Differs from a microcomputer in that it has no internal processing capabilities. Used to enter data into or retrieve processed data from a system or network.

Terminal Mode
An operational mode required for microcomputers to transmit data. In Terminal mode the computer acts as if it were a standard terminal such as a teletypewriter, rather than a data processor. Keyboard entries go directly to the modem, whether the entry is a modem command or data to be transmitted over the phone lines. Received data is output directly to the screen. The more popular communications software products control Terminal mode as well as enable more complex operations, including file transmission and saving received files.

The amount of actual user data transmitted per second without the overhead of protocol information such as Start and Stop bits or frame headers and trailers. Compare characters per second.

Portable modem company which USR acquired in 1991, therefore giving USRobotics its WorldPort product line.

Transmission Rate
Same as Bit Rate.

Transmit Data

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Universal Asynchronous Receiver- Transmitter. The controlling component of a serial port. There are three common types of UARTs: 8250, 16450, and 16550, which are capable of safe transmission speeds of 19,200 bps, 38,400 bps, and 57,600 bps respectively, though higher speeds are sometimes possible. Our internal modems have 16550 UARTs built in. External modems do not have UARTs.

One of many computer operating systems which are used to control a computer. UNIX was the main operating system of the Internet at one time. There are other operating systems used on the Internet however UNIX is still popular with many Web developers. UNIX is offered in many different varieties some are OSF, Version 7, Linux, Xenix, and GNU.

Fixes to existing code of the modem and there is no charge associated with updates.

User’s Network also referred to as “Newsgroups.” A large collection of discussion groups on all topics. Messages are posted to these groups as mail messages.

Uniform Resource Locator - Used to point to a particular internet site

Universal Serial Bus - Specification for increasing serial bus throughput.

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An ITU-T standard, included with V.34, that sends a signal to the receiving modem to make the process of connecting faster.

An ITU-T standard for facsimile operations that specifies modulation at 14.4K bps, with fallback to 12K bps.

V.21 190 Fax
An ITU-T standard for facsimile operations at 300 bps. USRobotics or compatible fax devices then transmit or receive at higher speeds.

V.21 190 Modem
An ITU-T standard for modem communications at 300 bps. Modems made in the U.S. or Canada follow the Bell 103 standard. However, the modem can be set to answer V.21 calls from overseas.

A ITU-T standard for modem communications at 1200 bps, compatible with the Bell 212A standard observed in the U.S. and Canada.

V.22 bis
An ITU-T standard for modem communications at 2400 bps. The standard includes an automatic link negotiation fallback to 1200 bps and compatibility with Bell 212A/V.22 modems.

An ITU-T standard for modem communications at 1200 bps with a 75 bps back channel. Used in the U.K.

An ITU-T standard for modem communications. Among other things, V.25 specifies an answer tone different from the Bell answer tone. All USRobotics modems can be set with the B0 command so that they use the V.25 2100 Hz tone when answering overseas calls.

V.25 bis
An ITU-T standard for synchronous communications between the mainframe or host and the modem using the HDLC or character-oriented protocol. Modulation depends on the serial port rate and setting of the transmitting clock source, &X.

V.27 terbo
An ITU-T standard for facsimile operations that specifies modulation at 4800 bps, with fallback to 2400 bps.

An ITU-T standard for facsimile operations that specifies modulation at 9600 bps, with fallback to 7200 bps.

An ITU-T standard for modem communications at 9600 bps and 4800 bps. V.32 modems fall back to 4800 bps when line quality is impaired, and fall forward again to 9600 bps when line quality improves.

V.32 bis
An ITU-T standard that extends the V.32 connection range: 4800, 7200, 9600, 12K and 14.4K bps. V.32 bis modems fall back to the next lower speed when line quality is impaired, and fall back further as necessary. They fall forward to the next higher speed when line quality improves.

V.32 terbo
Modulation scheme that extends the V.32 connection range: 4800, 7200, 9600, 12K, 14.4K, 16.8K, 19.2K, and 21.6K bps. V.32 terbo modems fall back to the next lower speed when line quality is impaired, and fall back further as necessary. They fall forward to the next higher speed when line quality improves.

An ITU-T standard that allows data rates as high as 28.8K bps. See V.8.

An ITU-T standard for modem communications that defines a two-stage process of detection and negotiation for LAPM error control. V.42 also supports the MNP error control protocol, levels 4.

V.42 bis
An extension of ITU-T V.42 that defines a specific data compression scheme for use with V.42 and MNP error control.

V.Fast Class (V.FC)
Proprietary modulation scheme developed by Rockwell International for data communication speeds up to 28.8K bps.

Voltage, Alternating Current

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Wide Area Network- A network that is not limited to a specific location. A WAN may link up several LANs together as one network.

WEP Encryption
Wired Equivalent Privacy (WEP), a security protocol for wireless local area networks (WLANs) defined in the 802.11b standard. WEP is designed to provide the same level of security as that of a wired LAN.

Wi-Fi is short for wireless fidelity. Wi-Fi is used in place of 802.11b in the same way that Ethernet is used in place of IEEE 802.3. A user with a Wi-Fi product can use any brand of access point with any other brand of client hardware that is built to the Wi-Fi standard.

Wireless Access Point
A wireless LAN transceiver that bridges a wired LAN to wireless devices.

Wireless PC Card
A wireless PC Card is a credit card-size memory or I/O device that fits into a personal computer, typically a laptop computer. Designed to provide connectivity via remote access, the PC Card is based on standards published by the Personal Computer Memory Card International Association (PCMCIA), an industry group organized in 1989 to promote standards for both memory and I/O integrated circuit card.

Wireless PCI Adapter
A wireless Ethernet adapter for each computer allowing the computers to interface with one another.

Wireless Router
A wireless device which passes information from one network to another.

Word Length
The number of bits in a data character without parity, start or stop bits.

Portable fax and data modems that are designed for business people who travel.

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The first of a family of error control software protocols used to transfer files between modems. These protocols are in the public domain and are available from many bulletin board services. Other related protocols are Ymodem and Zmodem.

Standard ASCII control characters used to tell an intelligent device to stop/resume transmitting data. In most systems typing <Ctrl>-S sends the XOFF character. Some devices, including the Courier, understand <Ctrl>-Q as XON; others interpret the pressing of any key after <Ctrl>-S as XON.

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X.75 defines the connection between public networks such as larger computers and mainframes.

Standard ASCII control characters used to tell an intelligent device to stop/resume transmitting data.

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