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Glossary of Terms
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AC - Alternating Current
The common form of elecrticity from power plant to home/office. Its direction is reversed 60 times per second in the US; 50 times in Europe.
AMI - Alternate Mark Inversion
A line encoding scheme for transmitting data bits over T1 transmission systems.
ANI - Automatic Number Identification
A feature in which a series of digits, either analog or digital, are included in the call, thus identifying the telephone number of the caller.
ANSI - American National Standards Institute
This organization organizes committees, made up of computer users, manufacturers, etc. to develop and publish industry standards.
ASCII - American Standard Code for Information Interchange
An asynchronous signaling code with character framing. An ASCII character consists of a start bit, seven data bits, a parity bit (even if unused), and a stop bit. In some cases, 1-1/2 or 2 stop bits are used. Note that 1-1/2 stop bits can not be used if the data will be carried by modern-day modems. The parity bit is used as an eighth data bit with able characters from 128 to 256. ASCII data can also be transported synchronously (aka clocked async).
Asynchronous Transmission
Digital signals are transmitted without precise clocking. the signals have different frequencies and phase relationships. Individual characters contained in the control bits (start and stop bits) designate the beginning and end of each character.
ATM - Asynchronus Transfer Mode
A component of ISDN. A switching technology that organizes digital data in 53 byte packets and transmits them using digital signal technology.
AUI - Attachment Unit Interface
A 15-pin connector and cable used to connect a network interface card and an Ethernet network.
Authentication
The process of attempting to ensure that the person using the computer system and performing tasks such as sending or receiving messages is one and the same as the person in whose name the account is registered. Networks require passwords as a means of authentication; however, passwords do not guarantee that the person using the system is the person to whom the password was given.
AWG - American Wiring Gauge
A US measurement standard of the diameter of non-ferrous wire, which includes copper and aluminum. The smaller the number, the thicker the wire. In general, the thicker the wire, the greater the current-carrying capacity and the longer the distance it can span.
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B8ZS - Binary with 8 Zero Substitution
Line code type, used on T1 and E1 circuits, in which a special code is substituted whenever eight consecutive zeros are sent over the link. Code is then interpreted at the remote end of the connection.
BER - Bit Error Rate
Ratio of received bits that contain errors.
Bipolar Violations
Violations of the electrical characteristic denoting a circuit with both negative and positive polarity.
bps - bits per second
The speed at which a point-to-point transmission line can convey data.
BRI - Basic Rate Interface
Basic ISDN service level that consists of two 64 Kbps B (bearer) channels that carry voice, data, and video along with one 16 Lbps D (delta) channel for signaling between telephone company switches and for carrying user-network messages. Also see ISDN.
Broadband Primary Card
This card resides in the N + 1 Protection Switch and is used to back up a T3 Application Module; it must reside in slot 8, 9, or 10.
Broadband Redundant Card
This card resides in the N + 1 Protection Switch and is used to back up a T3 Application Module; it must reside in slot 11.
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CHAP - Challenge Handshake Authentication Protocol
A type of authentication protocol in which the authentication agent sends the client program a key to be used to encrypt the user name and password. CHAP does not only require the client to authenticate itself at startup time, but sends challenges at regular intervals to make sure the client has not been replaced by an intruder, for instance, by switching phone lines. See also PAP.
CIR- Committed Information Rate
The maximum data rate that a Frame Relay network provider gurantees to transfer under normal network conditions, averaged over a minimum increment of time. CIR is either equal to or less than the full port speed. Measured in bits per second, CIR is one of the key negotiated cost factors in setting up a Frame Relay connection. See also EIR.
CLEC - Competetive Local Exchange Carrier
A company that creates and operates communication networks and provides customers with an alternative to the local telephone company.
CMOS - Complementary Metal Oxide Semiconductor
Technology employing integrated field-effect transistors in a complementary symmetry arrangement, which simulates "push/pull" operation because of the placement of opposing-polarity devices (p-channel and n-channel FET's).
CODEC - enCoder/DECoder
Chip used in the voice card to compress or decompress speech or audio signals
Controller Card
Provides communications between the DNX's System Manager and the N + 1 Protection Switch.
CPE - Customer Premises Equipment
Equipment, such as terminals and modems, supplied by the telephone company, that is installed at customer sites and connected to the telephone company network.
CRC - Cyclic Redundancy Check
A method of checking for errors in data that has been transmitted on a communications link. The dividend polynomial is initially preset to 0, and the 1s and 0s of the data stream become the coefficients of the dividend polynomial.
The division uses subtraction modulo 2 (no carries), and the remainder is transmitted as the error check field.
The receiving station compares the transmitted remainder with its own computed remainder, and an equal condition indicates that no error has occurred. The polynomial value depends of the protocol and code set being used.
CSA - Canadian Standards Association
A standards-defining organization founded in 1919.
CSU - Channel Service Unit
A device used to connect a digital phone line coming in from the phone company to network access equipment located on the customer premises. CSU may also be built into the netwrk interface of the network access equipment.
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D4 - Super Frame
A common framing type used on T1 circuits. It consists of twelve frames of 192 bits each, with the 193rd bit providing error checking and other functions. It is superceded by ESF but is still widely used.
DAC - Digital to Analog Converter
A device for converting digital signals into continuous analog signals. The converter usually buffers the input so that the output remains the same until the input changes. A typical converter provides two analog output channels ranging from 0 to 10+ volts with eight bits per channel resolution; also provides two logic level outputs for external device control.
DB Connector
A family of plugs and sockets widely used in communications and computer devices. DB connectors come in 9, 15, 25, 37, and 50 pin sizes. The DB connector defines the physical structure of the connector, not the purpose of each line.
DC - Direct Current
An electrical current that travels in one direction and is used within the computers eelctronic circuits.
DCE - Data Circuit-terminating Equipment
Device and connections of a communications network that comprise the netwrk end of the user-to-network interface. It provides physcial connection to the netwrok, forwards traffic and provides clocking signals used to synchromize data transmission between CTE devices itself
DCS - Digital Cross-Connect System
A network element providing automatic cross-connection of a digital signal or its constituent.
DDS - Dataphone Digital Service (previously Digital Data Service)
A digital network service available from At&T, the Bell Operating Companies and independent telephone companies. Non-switched synchronous data rates of 2400, 4800, 9600, and 56,000 bps, and switched synchronous 56,000 bps are available.
DHCP - Dynamic Host Configuration Protocol
Dynamically assigns IP addresses to client stations ocated on a TC/IP network at startup, and allows the addresses to be re-used when no longer needed. This allows a larger group of stations to share a limited pool of addresses.
DLCI - Data Link Connection Identifier
The number of a private or switched virtual circuit in a frame relay network. Located in the frame header, the DLCI field identifies which logical circuit the data travels over, and each DLCI has a committed information rate (CIR) associated with it. The DLCI number is local to the frame access device and frame relay switch it connects to, and it is generally changed by the switch within the network, because the receiving switch uses a different DLCI for the same connection.
DNS - Domain Name System
The manner in which the Internet locates and translates domain names into IP addresses.
Drop and Insert
A process of adding data (insert) to a T1 data stream, or terminating data (drop) froma T1 data stream to other devices connected to the drop and insert equipment.
DSO - Digital Signal Level 0
The base for the digital signal X series; transmits digital signals over a single channel at 64 Kbps.
DS1 - Digital Signal Level 1
Framing specification used in transmitting digital signals at 1.544-Mbps on a T1 facility (US) or at 2.108 Mbps on an E1 facility (Europe).
DS3 - Digital Signal Level 3
Framing specification used in transmitting digital signals at 44.736-Mbps on a T3 facility (US) or at 34.368 Mbps on an E3 facility (Europe).
DSL - Digital Subscriber Line
Technology that brings high-bandwidth information to homes and small businesses over copper telephone lines. It can carry both data and voice signals.
DSU - Data Service Unit
A device used in digital transmission that adapts a physical interface on a DTE device to a transmission facility such as T1 or E1. It is also responsible for functions such as timing.
DTE - Data Terminal Equipment
A device at the user end of a user-network interface that serves as a data source, destination, or both. It connects to a data network through a DCE device (such as a modem) and typically uses clocking signals generated by the DCE. It includes devices such as computers, protocol translators, and multiplexers.
DTMF - Dual Tone Multi Frequency
The signal a telephone company receives when a telephone's touch keys are pressed. Also known as Touchtone.
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E1
A digital transmission link with a capacity of 2.048 Mbps, used predominantly in Europe. E1 is channelized into 32 DSO's, each capable for carrying a single voice in conversation or data stream.
EBCDIC - Extended Binary Coded Decimal Interchange Code
A synchronous signaling code, commonly used by IBM, with no character framing (start/stop) bits and no parity bit. An EBCDIC character consists of eight data bits. It is used as one of many contiguous characters within a large block. The block contains start and stop bit sequences and an error control bit sequence. Also see Synchronous.
Echo
Async terminals use an "echo" to display entered characters on the screen. The echo can be remote (provided by the host computer) or local (within the terminal). A remote echo requires a full-duplex transmission facility while a local echo does not. Consequently, many terminals use the "FDX" terminology to configure for remote echo and the "HDX" terminology to configure for local echo. Failure to configure the host to complement the terminal will result in either no screen display (no echo) or double characters (two echos).
Also see Full-Duplex and Half-Duplex.
EIR - Excess Information Rate
The amount of data in excess of the CIR that can be transferred and is used for burst traffic support. Also see CIR.
Encapsulation
The process by which each protocol adds header information to a datagram. The header information included information regarding the source, destination and route of the message.
EIA - Electronic Industries Association
A membership organization that sets standards for the consumer products and electronic components.
E&M - Receive and Transmit
A trunking arrangement used for two-way switch-to-switch or switch-to-network connections. It is used with E1 and T1 interfaces.
ESF - Extended Superframce
A framing format for T1 applications that consists of twenty four frames of 192 bits each with the 193rd bit providing timing and other functions. It includes provisions for continuous monitoring by both the user and the telephone company central office. ESF provides a 4 Kbps link control channel (transparent to user data) which allows the telephone company to monitor the local loop, transmit and receive test messages and retrieve performance data, all without iterrupting normal operations.
Ethernet
The most widely-used standard for local are networks (LANs).
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FCC - Federal Communications Commission
United States government agency that supervises, licenses and controls electronic and electromagnetic transmission standards.
File Server
In a local area network (LAN), a computer that has been set aside to store frequently accessed files.
FPGA - Field Programmable Gate Array
A programmable logic chip in a high density of gates. There are a variety of FPGA architectures including programmable logic blocks, programmable interconnects and switches between the blocks.
Frame
At the data link layer in a point-to-point transmission line, the technique used to demarcate the data so that it can be received in an orderly and meaningful way.
Frame Relay
At the data link layer in a wide area network (WAN), a protocol for transferring packets at speeds up to 1.544 MBPS, depending on the physical medium being used. Frame Relay is designed for nosie-free digital lines, and therefore omits the error connection facilities. The result is increased bandwidth.
FTP - File Transfer Protocol
Application protocol used for trasnferring files between network nodes.
Full-Duplex - also known as FDW or Duplex
See Half-Duplex, Simplex, and Echo.
1) The ability of transmission facility to transport data in both directions simultaneously. Modems (or DSUs) at both ends of point-to-point full-duplex facilities and at the master location in the multipoint full-duplex facilities use "constant carrier." Modems at remote locations in multipoint full-duplex facilities use "controlled carrier" (carrier controlled by RTS with data transmission controlled by CTS). Also see Point-to-Point and Multipoint.
2) The ability of data processing device or protocol to simultaneously transmit and receive data. Note that some devices and protocols (e.g. BiSync) require full-duplex facilities but actually operate half-duplex.
FXO - Foreign Exchange Office
An interface that connects to the Public Switched Telephone Network's (PSTN) central office and is the interface offered on standard telephone. Exapmle: RJ-11 connector that allows analog connection to the central office.
FXS - Foreign Exchange Subscriber
An interface that connects directly to a standard telephone and supplies ring, voltage, and dial tone. Exapmle: RJ-11 connector allows connections to basic telephone equipment.
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Half-Duplex - also known as HDX
See Full-Duplex, Simplex, and Echo.
1) The ability of a transmission facility to transport data in both directions but not simultaneously. Half-duplex facilities use modems (or DSUs) configured for "controlled carrier," also know as "switched carrier," (carrier controlled by RTS with data transmission controlled by CTS) at all locations.
2) The ability of a data processing device or protocol to transmit and receive data but not simultaneously. Note that some devices and protocols (e.g. BiSync) require full-duplex facilities but actually operate half-duplex.
HDLC - High-Level Data Link Control
An ISO communication protocol used in X.25 packet switching networks. It provides error correction at the data link layer.
HDSL - High-Bit Rate Digital Subscriber Line
The earliest variation of DSL. It is used for wideband digital trasmission within a business and between the telephone company and a customer. HDSL is symmetrical meaning an equal amount of bandwidth is available in both directions.
Host
A computer that can function as the endpoint of a data transfer. The computer can be a sindle-user personal computer or workstation that is part of a local area network (LAN), a minicomputer, or a mainframe computer. The term "node" is synonomous with host.
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IC - Integrated Circuit
An integrated circuit (IC), sometimes called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated. An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor. A particular IC is categroized as either linear (analog) or digital, depending on its intended application.
ICMP - Internet Control Message Protocol
A protocol used between a host server and a gateqay to the Internet to send message control and error-reporting messages.
Interface - One "side" of a pair of connected devices, i.e., 1) the DCE side or the DTE side 2) the signaling specification used by a pair of connected devices.
IP - Internet Protocol
The method by which data is sent from one computer to another on the Internet. It is a connection- less protocol, meaning there is no established connection between the two computers. Data is sent as independent packets, also known as data units or data grams, which are contained in the IP address, a 32-bit number that identifies each sender or receiver of information. When the packets are received, they are put into the correct order by the Transmission Control Protocol (TCP).
IPX - Internetwork Packet Exchange
A NetWare communications protocol used to route messages from one node to another. IPX packets include net-work addresses and can be routed from one network to another.
Interface Care (Module)
A computer circuit board, card or module that is installed in a computer so that it can be connected to a network.
ISDN - Integrated Service Digital Network
A system that provides simultaneous voice and high speed data transmission through a single channel to the user's premises. ISDN is an international standard for end-to-end digital transmission of voice, data, and signaling.
ITU-T - International Telegraph and Telephone Consultative Committee
International body that develops worldwide standards for telecommunications technologies.
IXC - Inter-exchange Carrier
A common carrier providing long distance connectivity between local telephone areas. Includes AT&T, MCI, and Sprint.
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Kbps
Kilobits per second or one thousand bits per second.
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LAN - local area network
A computer network that links personal computers and workstations within a limited geographical area, such as a building or several contiguous buildings. Linked by cables such as coaxial cables or twisted pair, the computers connected to the LAN can access resources on other computers and shared peripheral devices. If there is a central network device, it is a file server that includes resources of use to all. To keep two workstations from accessing the LAN at the same time, LANs employ a Medium Access Control (MAC) protocol; ethernet is one such protocol.
Leased Line
A permanently connected telephone line that links a host to a service provider. Typically, leased lines can handle between 56,000 and 64,000 bits per second of data. Larger host systems require T1 lines (1.544 Mbps) or T ines (45 Mbps).
LED - Light Emitting Diode
A display technology that uses a semiconductor diode that emits light when charged.
Loopback
A method of checking the accuracy of data transmission in shich the transmitted data stream is returned, or looped back, to its source for comparison with the original data. Loopbacks can be performed on data in an analog or digital state.
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MAC Header
In Open Systems Interconnection (OSI) Reference Model, a sub layer that was added between the physical layer and the data link layer; this sub layer describes the protocol for broadcast networks (i.e. LANs).
Mbps
Megabits per second or one million bits per second.
MIB - Management Information Base
A directory listing information that is used and maintained by a network's management protocol, such as SNMP.
Modem - Modulator-Demodulator
A device that adapts a terminal or computer to a coice-grade telephone line. At the source, a modem converts digital signals to form suitable for transmission over analog communication facilities. At the destination, the analog signals are returned to their digital form. Modems are avaialable that are synchronous or asynchronous for either 2-wire dial or 4-wire leased line applications. See also Asynchronous and Synchronous.
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N + 1 Device Redundancy (NDR)
A spare or redundant device is provided to replace a failed primary device in a group.
N + 1 Device redundnacy Group (NDRG)
A collection of configured primary devices and a redundant device that will be used for redundancy.
Narrowband Primary Card
This card resides in the N + 1 Protection Switch and is used to back up an Octal T1/E1 Application Module; it must reside in slot 1.
NAT - Network Address Translation
A method for translating internal IP addresses or network addresses into a single globally unique IP address. It permits a nearly unlimited number of users of one class C Network address because global addresses are required only when a user is connected to the internet. It also serves as a fire wall by keeping individual IP addresses hidden from the outside world. NAT is configured by defining address pools and spcifying wheter a port is "Inside" or "Outside." Also see IP.
NEBS - Network Equipment Building Systems
Adhering to standards from Bellcore for equipment used in Telco central offices (COs). IT provides stringent specifications fro durability, grounding, cables, and hardware interfaces.
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OSPF - Open Shortest Path First
OSPF is a routing protocol that determines the best path for routing IP traffic over a TCP/IP network. It uses less router-to-router update traffic than the RIP protocol that it has been designed to replace.
Overhead
Framing, error control, addressing, idle coode, or any other characters or bit sequences in a data transmission orther than actual end-user data.
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Packet
Also known as data unit or datagram. A unit of data that has been broken down into a small enough size so that the Internet Protocol can handle it and transport it.
PAP - Password Authentication Protocol
PAP is the most basic form of authentication for logging into a network. A user's name and passwork are transmitted over a network and compared to a table of name-password pairs. Typically, the passwords stored in the table are encrypted. Also see CHAP.
Parity
A character-level error-control mechanism used with asynchronous signaling codes. A parity bit is set to either a "one" (mark) or a "zero" (Space) to ensure that the total quantity of "ones" within a character are either odd (odd parity) or even (even parity). Start and stop bits are excluded from the parity calculation. Character-level error-control has bot been successful, and today, parity is rarely used. Asynchronous hardware, however, requires that the parity bit be present (usually forced to "one") even if unused.
PCM - Pulse Coded Modulation
Transmission of analog information in digital form through sampling and encoding the samples with a fixed number of bits.
PCS - Personal Communication Service
A network that provides personal, terminal and service mobility. Includes broadband and narrowband in the United States.
PING - Packet Internet Groper
A diagnostic utility program that indicates whether a remote host is actually connected to the network.
PLAR - Private Line Auto Ring
A leases voice circuit that connects two single stations. See Full-Duplex.
Point-to-Point
A communications link connecting two and only two stations. See Full-Duplex
Point-to-Point Network
A network in which a message originates from one node and travels to one or more destination nodes, but not to every node on the network. Wide area networks (WANs) are point-to-point networks, while most local area networks (LANs) are broadcast networks that send all network data to every computer connected to the LAN.
Polling
Interrogation of devices for purposed such as to avoid contention, to determine operational status, or to determine readiness.
PPP - Point-to-Point Protocol
A protocol at the data link layer used for dialup IP access. It establishes a temporary but direct connection in which packets of data can travel directly from and to a node. PPP offers data compression, data negotiation and error correction.
Primary Device
A device in an NDRG that would normally carry traffic
Primary Slots (N + 1 Protection Switch)
Holds Interface Cards for the cards plugged into the DNX's
Primary Slots (DNX)
Cards plugged into these slots are considered active and online under normal operation.
Protected Device
This is a promary device that will be replaced by a redundnat device should it fail within its NDRG
Protocol
A standard that governs the operation of a network communications function by providing a clear-cut set of rules for its operation as well as the specific programs that are designed to implement these rules. Specific protocols apply to each layer in a network's architecture.
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Redundant Device
One device in an NDRG that has been configured to replace or substitute for a failed primary device in the NDRG.
Reverse Channel
The RS232 specification assumes that normal transmit and receive data (pins #2 and #3) will be at identical rates. However, the specification also includes a full complement of secondary data and control signals (but no clocks) for additional data transport, typically at rates from 5 to 75 bps. The need for these secondary channels no longer exists but, when it did, a half duplex facility was configured to operate as simplex facility with a scondary channel in the opposite, or reverse, direction (hence, "reverse channel"). Also see half-duplex and simplex.
Restore
An action that occurs when traffic is returned to the primary device that was being protected in the NDRG by a redundant device.
RFC - Request for Comments
The document series maintained by the Internet community that records the protocols within the Internet and gives other information.
RIP - Routing Information Protocol
A simple routing protocol that is part of the TCP/IP protocol suite. It determines a route based on the smallest hop count between source and destination. RIP is a distance vector protocol that routinely broadcasts routing information to its neghboring routers and is known to waste bandwidth.
ROHS
Restriction of Hazardous Substances in electrical and electronic equipment. This directive was established by the European Community.
Router
An electronic device that connects a local area network (LAN) to a wide area network (WAN) and handles the task of routing messages between the two networks.
RS232
An electrical signaling specification published by the Electronic Industries Associations (EIC). Although not identified in the specification, the 25-pin (DB25) connector, with specific pin assignments, is commonly accepted as "the RS232 connector." The DNX supports RS232 on the Octal High Speed Module's DB25 connector via industry-standard pin assigments.
RS520, RS449, RS422/422A
These are all signaling specifications published by the Electronic Industries Association (EIA). RS422 defines electrical signaling characteristics. It references a companion standard RS449 that defines signal functions places on a 37-pin (DB37) mechanical connector with specific pin assignments. Because of the cost of the DB37 connectors, manufacturers generally ignored that portion of the specification and placed a subset of the RS449 signals on a 25 pin (DB25) connector. The EIA subsequently legitimized this practice by publishing RS422A/RS530. A practical matter, RS530 is simply "RS449 on DB25."
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SDSL - Single-line Digital Subscirber Line
One of four DSL technologies. SDSL delivers 1.544 Mbps both downstream and upstream over a singel copper twisted pair. the use of a single twisted pair limits the operating range of SDSL to 10,000 feet (3048.8 meters).
Simplex
A data processing device or protocol capable of transmitting or receiving but not both. Simplex devices are rare in data processing applications. One example is printing via the obsolete "202" modem. In dial mode, the 202 was Half-Duplex and printer flow control could not get back to the computer fast enough. The Printer was configured as Simplex with a reverse channel for flow control. Simplex exapmles in other industries include commercial radio and television. See Full-Duplex, Half-Duplex, and Reverse Channel.
SLIP - Simple Network Management Protocol
Network management protocol used in TCP/IP netwokrs. SNMP monitors and controls network devices, and manages configurations, statistics collection, performance and security.
SONET - Synchronous Optical Network
A high speed (up to 2.5 Gbps), fiber-optic transmission system for digital traffic. SONET uses time division multiplexing (TDM) to send multiple data strams simulatneously. STS1 is the basic building block of SONET.
Standby Slots (N + 1 Protection Switch)
Holds Interface Cards for the cards plugged into the DNXs standby slots.
Standby Slots (DNX)
Cards plugged into these slots are considered inactive and offline under normal operation. They become active and go online when a card plugged into the primay slot becomes non-operational.
STS1 - Synchronous Transport Signal Level 1
Basic building block signal of SONET, operating at 51.84 Mbps. Faster SONET rates are defined as STS-n, ehre n is a multiple of 51.84 Mbs.
Switchover
An action that occurs when a redundant device replaces a primary device that failed.
Synchronous Transmission
Digital signals are transmitted with precise clocking. Signals have the same frequency. Individual characters contained in control bits (start and stop bits) designate the beginning and end of each character.
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T1
A high-bandwidth telephone trunk line with a capacity of 1.544 Mbps, used in NOrth America. T1 is channelized into 24 DSOs, each capable of carrying a single voice conversation or data stream.
TCP - Transmission Control Protocol
The method used with the Internet Protocol (IP) to send data in the form of packets between computers over the INternet. TCP is responsible for dividng a message into packets that the IP can use, and for reassembling packets into complete message.
TDM - Time Division Multiplexing
A technology that transmits multiple signals simultaneously over a single transmission path. Each lower speed signal is time sliced into one high speed transmission.
Telnet
A user command and an underlying TCP/I{ protocl for accessing remote computers.
TFTP - Trivial File Tranfer Protocol
Network application tht is simpler than the File Transfer Protocol (FTP) but less capable. USes the USer Datagram Protocol (UDP)
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UDP - User Datagram Protocol
A connection-less, communication transport method that offers a limited amount of service when messages are exchanged over the INternet Protocol. It is an alternative to TCP. Unlike TCP, UDP does not acknowledge or guarantee delivery, nor does it provide sequencing of packets.
V.35
An electrical signaling spcification published by CCITT. Although not identified in the specification, the M-series, 34-pin (Winchester-type_ connector, sith specific pin assignments, is commonly accepted as "the V.35 connector." V.35 signaling is also legitimately supported on DB25 connectors but the pin assignments have not been standardized within the industry. The DNX Test Access Module supports V.35 per industry standards.
V.54
An ITU standard for various loopback tests that can be incorporated into modems for testing the telephone circuit and isolating transmission porblems. Operating modes include local and remote digital loopback and remote analog loopback.
Virtual Tributary (VT)
A signal desinged for transport and switching of pay-oads smaller than the STS1 rate. All services below DS3 rate are transported in the CT structure. T1 payloads are equivalent to a VT1.5, while E1 payloads are euqivalent to a VT-2.
WEEE Directive
Waste Electrical and Electronic Equipment for the European Community
WAN - Wide Area Network
A communications network that is capable of spanning a geographic area larger than a metropolitan area.
Workstation
A computer that is connected to a network. A workstation has its own processor, processes applications locally and may access data and resources located elsewhere on the network.
X.21
An electrical standard published by the CCITT that includes a 15-pin (DB15) mechanical connector identification with specific pin assignments.
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