Broadband Glossary



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

A

.au
A sound file format for UNIX systems.

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.

ADSL (Asymmetric Digital Subscriber Line)
ADSL is a truly fast, always on, Internet connectivity running through existing telephone lines. ADSL can transmit more than 6 Mbps to a subscriber providing transmission capabilities such as Internet access, video-on-demand, and LAN access.

Adapter
A standard term used as shorthand for network adapter card, sometimes also called a Network Interface Card (NIC).

Analog
A general class of devices or circuits in which the output varies as a continuous function of the input.

Analog Signals
Continuous, varying waveforms such as the voice tones carried over phone lines. Contrast with digital signals.

ATM
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).

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.

Authentication Header (AH)
Used to provide connectionless integrity and data origin authentication for IP datagrams, and to provide protection against replays. This latter, optional service may be selected, by the receiver, when a Security Association is established. AH provides authentication for as much of the IP header as possible, as well as for upper level protocol data. AH may be applied alone, in combination with the IP Encapsulating Security Payload, or in a nested fashion through the use of tunnel mode.


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B

Bandwidth
This is the amount of data that can be transmitted over a given time period.

Baud Rate
The number of discrete signal events per second occurring on a communications channel. The communications carrier frequen- cy. Due to advanced coding methods, each signal can carry more than one bit. At 300 baud, approximately 300 bits are trans- mitted 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 computerís serial port rate.

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.

Beta Tester
An outside source who performs preliminary testing.

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.

Bit-mapping
A technique that lets one decimal number (in this case, a number between 0 and 255) stand for up to 8 separate binary settings.

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 (bps)
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.

Broadband
This is the communication channel. The bandwidth corresponds to the difference between the lowest and highest frequency signal which can be carried by the channel.

Broadband Modulation
The radio signal transfer minimal rate of speed through the broadband.

Buffer
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.

BUS
A LAN topology in which all the nodes are connected to a single cable, considered equal, and receive congruent signals.

Bus Topology
The linear LAN used by Ethernet networks.

Byte
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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C

Cable
In the context of computer data transfer, a technology which enables data to be carried over coaxial television cable. Existing cable services are very fast, but asymmetric, and the bandwidth of a given cable connection is shared among several users. A cable modem provides users with high-speed Internet access through a cable television network at more than 1 Mbps. Cable modems are typically external devices that are placed next to your computer. Cable modems typically connect to computers through a standard 10Base-T Ethernet interface. Unlike DSL, which provides point-to-point traffic to the ISP, cable is a shared network in that end users within an area are sharing the line.

Carrier
The basic signal altered or modulated by the modem in order to carry information. 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.

Cache
A cache is an interval of high-speed memory at the precise border between a network and the Internet. The cashe holds frequently accessed Internet information so that when accessed again, the retrival time is significantly reduced.

Challenge Handshake Authentication Protocol (CHAP)
A network server sends the client program a key that can encrypt the username and password. Using this protocol, the username and password can be transmitted in an encrypted form that protects against hackers or other intruders.

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.

Characters per second (CPS)
A data transfer rate generally estimated from the bit rate and the character length. For example, at 2400 bps, 8-bit characters with start/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 error-control protocols, employ advanced techniques such as longer transmission frames and data compression to increase CPS.

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.

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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D

DHCP (Dynamic Host Configuration Protocol)
This is a protocol for automatic TCP/IP configurations providing static and dynamic address allocation and management.

DNS (Domain Naming System)
This is a mechanism used in the Internet for translating names of host computers into addresses.

DSLAM (Digital Subscriber Line Access Multiplexer)
This is a network device that receives signals from multiple customer Digital Subscriber Line connections and places them on higher speed lines with multiplexing techniques for the fastest phone line technology available.

DSP (Digital Signal Processor)
Frequently called the ďdata pump.Ē A chip in the modemís circuitry that handles all of the actual work of sending and receiving data.

Default Gateway
When setting up the PC to operate with a Pipeline, the gateway setting (in the Network settings) must be set to the IP address of the Pipeline. Using the IP address of the Pipeline as the gateway, lets your computer know that you will use the Pipeline to access remote networks.

DOCSIS
Data Over Cable Service Interface Specifications (DOCSIS) specifies modulation schemes and the protocol for exchanging bidirectional signals over cable. It supports downstream data rates up to 27 Mbps. Downstream data rate transfers range between 1.5 to 3 Mbps, depending on TI connection status.

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


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E

EMI (Electromagnetic Interference)
Noise generated by the modem (or any electronic device).

Encapsulation
Encapsulation is a method that involves wrapping a header around a node of information, usually in the form of an IP packet.

Encryption
Encryption is a method that translates private or sensitive data into a private code.

Encryption Type
This is the mathematical process whereby encoding information is created for the purposes of ciphering data.

Ethernet
The most popular LAN technology in use today. Ethernet sends its communications through radio frequency signals carried by coaxial cables, unshielded twisted pairs, or optical fibers. Ethernet uses a bus or star topology and supports data transfer rates of 10 Mbps. A newer version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps. And the newest version, Gigabit Ethernet supports data rates of 1 gigabit (1,000 megabits) per second.

Ethernet Meltdown
An event that causes saturation, or near saturation, on an Ethernet. It usually results from illegal or misrouted packets and typically lasts only a short time.


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F

Fiber Optics
Thin tubes of glass designed to carry or transmit light waves of band frequencies.

Filter
This is an operating parameter used in LAN bridges and routers that when set, will cause these devices to block the transfer of packets from one LAN to another.

Firewall
A firewall protects your network from malicious attacks targeting Broadband users. It prevents people from accessing your information and using your computer without your knowledge.

Flash Memory
A form of memory that can be electrically erased and reprogrammed without the need to remove it from the circuit board.

Frequency
The number of times a complete electromagnetic wave cycle occurs per second.

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

Flow Control
A mechanism 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.

Frame
A data communications term for a block of data with header and trailer information attached. The added information usually includes a frame number, block size data, error-check codes, and Start/End indicators.

Full Duplex
Signal flow in both directions at the same time. In microcomputer communications, may refer to the suppression of the online Local Echo.


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G

G.lite
Officially known as G.992.2, it is now a standard way to install Asymmetric Digital Subscriber Line service. G.lite makes it possible to have Internet connections to home and business computers at up to 1.5 Mbps over regular phone lines.

G.dmt
This refers to the ADSL standard approved by the International Telecommunications Union (ITU). G.dmt indicates full rate ADSL which provides standards for higher speed ADLS than G.lite. G.dmt provides maximum data rates of 8 Mbps downstream to the subscriber and 1.5 Mbps upstream from the subscriber.

GigaHertz (GHz)
One billion cycles of electrical frequency per second.


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H

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.

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


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I

IAD (Integrated Access Devices)
A residential gateway connecting userís computer, printer, microphone, speaker, phone, TV etc with Internet though broadband connections.

IP (Internal Protocol)
This allows a packet of information to travel through many networks and LANs.

IPsec (Internet Protocol Security)
IPsec utilizes Virtual Private Networks (VPNs) for the purposes of allowing for remote user access through dial-up connection to private networks.


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J

Jumper
A switch composed of pins and a shunt. The shunt's position on the pins determines the jumper setting.

Jukebox
Personal Digital Entertainment or Jukebox leverages the power of the PC to create enhanced audio and video entertainment experiences in a compact form. On a portable big storage capacity (miniHardDiskDrive) allows to store WAV, MP3, news, digital audio books, various data, transferring via mic, line-in, data link.


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K

K
When used as a "computer" measure, such as K Bytes of memory, represents the numeric value 1024.

Ka Band
Portion of the electromagnetic spectrum in the 18 to 30 gigahertz per second range.

K-bit
An encoded transmission bit (produced by differential manchester encodation) which does represent data and is used only for transmission control.

K-carrier System
Transmission system providing 12 voice telephone circuits on a bandwidth up to 60 kilohertz.

Kermit Protocols
A set of software implemented data link and higher level protocols developed to facilitate file transfer. The software was written at Columbia University and is in the public domain thus it is cheap to acquire.

Kernel
When referring to system software it is the software which interfaces directly to the hardware. For example the ISO/OSI session level kernel interfaces other session level software with the hardware.

Key Management
The process of managing the keys used for data encryption.

Key Telephone Set
A telephone set using "push button" keys to provide a variety of services.

Keyboard Send/Receive (KSR)
A combination data transmitter/receiver which is limited to printer receive and keyboard transmit.

Keying
1) The modulation of an analog signal to carry digital information. 2.) The interruption of a DC circuit for the purpose of Signaling information.

Kilobit
One thousand bits.

Kilohertz
One thousand hertz or one thousand cycles per second.

Ku Band
A popular satellite communications frequency band. The range is 10-12 giga hertz


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L

LAN (Local Area Network)
This is a network base covering a local geographic area usually used by businesses. LANs are capable of transmitting data faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.

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.

Layer 2 Tunneling Protocol (L2TP)
L2TP is an extension to the Point-to-Point Protocol (PPP), which is utilized with Virtual Private Networks (VPNs). L2TP supports multiple protocols and unregistered and privately administered IP addresses over the Internet. This allows enterprise customers to outsource dialout support, thus reducing overhead for hardware maintenance costs and 800 number fees, and allows them to concentrate corporate gateway resources.

Low-pass Filter
A low-pass filter is a device that cuts frequencies off above a certain point and allows all other frequencies to pass.


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M

MegaHertz (MHz)
One million cycles per second.

MODEM (Modulator/Demodulator)
A device that converts data to a form that can be transmitted as a telephone to data processing equipment, where a similar device reconverts it. The Courier is a telephone channel modem that modulates, or transforms, digital signals from a computer into the analog form that can be carried successfully on a phone line. It also demodulates signals received from the phone line back to digital signals before passing them to the receiving computer.

Modulation Type
A modulation is the process of varying characteristic elements of the electrical carrier waves.

Multiple System Operator (MSO)
A company that owns and operates more than one cable system.

MUX
Multiplexor, allows multiple devices to share a single pathway.


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N

NetBEUI
This is a networking protocol requiring minimal or no configuration.

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.

NIC (Network Interface Card)
A Network Interface Card (NIC) is a computer circuit board that is installed in a computer so that it can be connected to a network. Most NICs are designed for a particular type of network, protocol, and media. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or token ring.

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


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O

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.

Optical Fiber
An extremely thin, flexible thread of pure glass, able to carry one thousand times the information possible with traditional copper wire.


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P

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.

PC Card
A 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.

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.

POP
Point to Point. The point where the inter-exchange carrier's responsibilities for the line begin and the local exchange carrier's responsibility ends.

Point of Presence. A telephone number that gives you dial-up access. Internet Service Providers (ISPs) generally provide many POPs so that users can make a local call to gain Internet access.

Point to Point Tunneling Protocol (PPTP)
PPTP allows corporations to extend their own corporate network through private "tunnels" over the public Internet. This is also known as a Virtual Private Network (VPN).

POTS (Plain Old Telephone Service)
This is a basic voice service available in residences throughout the United States.

Protocol
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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Q

Queue
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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R

RAM (Random Access Memory)
The primary memory in a computer, this is memory that can be overwritten with new information. The random access part of its name comes from the fact that the next bit of information in RAM can be located - no matter where it is - in an equal amount of time.

Ring
A network topology in which the nodes are connected in a closed loop.

Read-Only Memory (ROM)
Permanent memory, not user-programmable. The Courier V.Everything modem's factory settings are stored in ROM and can be read (loaded) into RAM as an operational configuration if DIP switch S10 is ON at power on.

RJ-11
Technical name for a standard phone cable used by telephones and modems. One RJ-11 cable is supplied with each of our desk- top modem products. This is a six-conductor modular telephone jack wired for up to four wires. The most common telephone jack in the world, the RJ-11 is typically used for connecting telephone instruments, modems, and fax machines to a female RJ-11 jack on the wall or in the floor.

RJ-45
The type of connector used to connect the Access Point to a wired NIC, router, or hub.

Router/Home Gateway A device which allows your Internet connection to be distributed to multiple computers via an Ethernet hub. The Router/Home Gateway also can provide a level of security for the network through the use of a firewall.


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S

Satellite Internet Access
Satellite Internet Access is just as it sounds; a one-way or two-way option to access the Internet using satellite technology as the means of data transfer.

SDLC (Synchronous Data Link Control)
A protocol developed by IBM for software applications and communicating devices operating in IBMs.

SDSL
Symmetric Digital Subscriber Line (SDSL) transfers data over existing copper telephone lines up to 3 Mbps. To take advantage of SDSL, a subscriber must have a special SDSL modem. SDSL is called symmetric since it supports the same data transfer rates for both upstream and downstream traffic.

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 computerís serial ports are run by UART chips, which come in different speeds.

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

Splitter
As its name suggests, a Splitter separates the ADSL service from the telephone service. The Splitter plugs into your existing telephone socket. You then plug your existing telephone cable into the designated socket, and the connection to your USB ADSL modem or Ethernet router into the socket that remains free.

Subsplit
A frequency division scheme that allows bi-directional traffic on a single cable.


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T

TCP/IP (Transmission Control Protocol/Internet Protocol)
This is a set of protocols designed to link dissimilar computers using a variety of networks and LANs.

Terminal
A device whose keyboard and display are used for sending and receiving data over a communications link. Differs from a micro-computer or a mainframe in that it has little or no internal processing capabilities.

Throughput
The amount of data transmitted between two points in a given amount of time.

Topology
The geometric physical or electrical configuration describing a local communication network. The most common distribution system topologies are the bus, ring, and star.

Trunking
Transporting signals from one point to another.


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U

UART (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.

URL (Uniform Resource Locator)
A URL identifies the address, or location, of a resource on the Internet (Web site).

USB (Universal Serial Bus)
This is a new external bus standard that supports data transfer rates of 12 Mbps.

USB Adapter
A USB Adapter is a physical device that allows one hardware or electronic interface to be adapted to another hardware or electronic interface.


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V

VCI (Virtual Channel Identifier)
This is the address of a virtual circuit.

VPI (Virtual Path Identifier)
This is the address of a virtual path corresponding to a connection on an ATM Network.

Virtual Private Network (VPN)
A virtual private network (VPN) is a private network designed to promote and maintain privacy through the employment of tunneling protocols.

VDSL
Very High Speed Digital Subscriber Line (VDSL) transmits data between 1000 and 4500 feet (300 - 1500 meters) up to 50 Mbps through twisted pair copper wire. The rule with VDSL is the shorter the distance, the faster the connection rate. VDSL users enjoy the maximum bandwidth available through normal phone lines.


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W

WAN (Wide Area Network)
This is a network base covering a large geographic area.

WINS (Windows Internet Name Service)
This is a service transposing Windows networking names into useable addresses for routing purposes.


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X

X-Modem
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
Y-Modem and Z-Modem.

X-on X-off Protocol
An extension of the TTY protocol which uses additional Transmission On (X-on) and Transmission Off (X-off) characters to accommodate differences in speed between the transmitter and the receiver.

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


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Y

Y-Modem
Error-free file transfer protocol that can be used on error-corrected links and to transfer multiple files with a single command.


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Z

Z-Modem
Error free file transfer protocol that supports multiple file transfers, plus many other advanced features.

Zero Bit Insertion
A technique whereby additional "zeros" are inserted after a fixed number of "ones" in a transmission sequence to ensure that data will not be misinterpreted as controlling information.

Zero Byte Time Slot Interchange (ZBTSI)
A control technique used in specific T1 systems in which information on the location(s) of all-zero bytes is contained in a defined area of the transmission frame.

Zero Code Suppression
A technique used to prevent the existence of eight consecutive zeros in a digital transmission frame. A number of different schemes are used. The process is essential for the proper operation of most T1 digital transmission systems.


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