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Glossary Of IT Terms

1000Base-LX/FX Gigabit Ethernet over fiber optic cable.
1000Base-T 1000Mbps, 1 Billion bits per second over copper cabling. All four pairs of Cat6 cable utilized at 250Mbps per pair.
100Base-FX 100 Mbps Ethernet data transmissions over Fibre optic cable
100Base-LX 1300nm - Long wavelength fiber optic transmissions at 100 Mbps.
100Base-SX 850nm - Short wavelength fiber optic transmissions at 100 Mbps.
100Base-T2 100 Mbps Ethernet running base band signaling over two twisted pairs
100Base-T4 Four pairs of Cat3 or better cable. Transmits at 25 Meg on all four pairs.
100Base-TX 100 Mbps Ethernet running base band signaling over twisted pair copper. Full duplex
10Base-2 Thin Ethernet, sometimes called thin net or coax, capable of data transmissions up to 185 meters.
10Base-5 Thick Ethernet cable capable of data transmissions up to 500 meters.
10BaseT 10 Mbps Ethernet running base band signaling over twisted pair copper cable
62.5/125 micron The common size of fiber optic cables
ACR Attenuation to Crosstalk Ratio. The level of cross talk in relationship to the attenuated signal at the far en of the cable. Critical in Full Duplex mode.
ADSL Asymmetric Digital Subscriber Line. A digital connection with higher bandwidth for down loading than up loading.
Alien Crosstalk Crosstalk from an adjacent cable or cables
ANSI American National Standards Institute.
ARCnet Attached Resource Computer Network. A low speed 2.5Mbps developed by Data point.
ASCII American Standard Code for Information Interchange. Originally a 7 bit code later 8 bit for communication interfaces.
ASIC Application Specific Integrated Circuit. An IC built to perform a specific task
Attachment cable The cable between the wall socket and active equipment usually a PC or DTE.
Attenuation Loss of signal strength and integrity over a given length of cable
AUI Attachment User Interface. An IEEE 802.3 standards 15 pin 3 row 'D' type connector interface.
AWG American Wire Gauge. The larger the number the smaller the wire diameter.
Balanced cable Two identical wires carrying signal of opposite polarity but equal amplitude to eliminate interference. The wires are twisted to maintain balance over a distance.
Balun Balanced - unbalanced impedance matching connector. Connects balanced and un-balanced network cables together.
Bandwidth The capacity of a medium to carry data bits. Measured in Hz
Base band The raw data is transmitted using the full bandwidth of the cable with no modulation.
BAUD Number of signal or voltage changes per second. Sometimes relates to Bps but not always.
BNC Bayonet connector used with RG58 coaxial cable networks. Thin Ethernet
bps Bits per second
Broadband The bandwidth of the cable is split into multiple modulated channels. Guard bands are used to separate the channels
Broadcast To send data to more than one device at a time
Bus Network A network with all devices sharing one common cable.
CAT5 100 MHz Category 5 data cabling as specified by the EIA/TIA standards authority
CAT5 E Enhanced Cat 5 data cabling with more stringent tests and headroom. Still 100Mhz
Category 1, Cat1 Unshielded Twisted Pair for use as speaker or door bell wire.
Category 2, Cat2 UTP for frequencies up to 1.5Mhz. Used in analogue telephone applications.
Category 3, Cat3 UTP for frequencies up to 16Mhz. 100 ohms.
Category 4, Cat4 UTP 100 ohm for frequencies up to 20Mbs defined by TAI/EIA 568-A specifications.
Category 5, Cat5 UTP 100 ohm for frequencies up to 100Mbs defined by TAI/EIA 568-A specifications.
Category 5E, Cat5E Enhanced Cat5. Similar to Cat5 with improved specifications including PSELFEXT, ACR and attenuation. Defined by EIA/TIA 568-A-5.
Category 6,Cat6 Proposed cabling standard to support up to 250 MHz over UTP. Not yet ratified.
Category 7, Cat7 Proposed cabling standard to support up to 600 MHz over UTP.
CDDI Copper Distributed Data Interface as defined by (ANSI X3T12) for 100Mbs token passing over copper twisted pair.
Class 'C' ISO/IEC 11801cabling standard corresponding to the EIA/TIA Cat3 cabling standards
Class 'D' ISO/IEC 11801cabling standard corresponding to the EIA/Tia Cat5 100Mhz cabling standards
Class 'E' ISO/IEC proposed cabling standard corresponding to the EIA/Tia Cat6 250Mhz cabling standards
Coax Coaxial cable with a copper screen carrying unbalanced signals
Collision domain All the nodes on an Ethernet segment that are affected by data collisions. Switches and bridges break up networks into individual collision domains
Core Centre of a fiber optic cable
Crosstalk interference picked up from an adjacent wire pair within the same cable (see also alien crosstalk)
CSMA/CD Carrier Sense Multiple Access with Collision Detect. A NIC transceiver "listens" to the network before transmission and can detect collisions.
D' Type D' Shaped connector with an array of pins in 9, 15 and 25
Drop Single cable outlet
Drop Cable The cable from the wall socket to the network device, usually a PC or DTE
DTE Data Terminal Equipment. RS232 description of a terminal or PC.
EIA Electronics Industry Association in America
EIA 568 UTP commercial building specifications from the EIA
EIA 568B Now the most common UTP cable colour codes and pin allocation
ELFEXT Equal Level Far End Cross Talk
EMI Electro Magnetic Interference. Unwanted noise from a source such as fluorescent lighting and electric motors
Ethernet A LAN protocol in which computers access the network through CSMA/CD protocols defined by the IEEE 802.3 standards. Invented by Rank Xerox
Fast Ethernet 100Mbps CSMA/CD Ethernet
FDDI Fiber Distributed Data Interface as defined by (ANSI X3T12) for 100Mbs token passing over Fibre.
FOIRL Fiber Optic Inter-Repeater Link. An Ethernet fiber optic connection method intended for connection of repeaters
Frame Relay Efficient method of packaging data into variable size frames for transmission over networks
Full duplex Allows data transmissions in two directions at once. Transmit and receive simultaneously
Gbpg Giga bits per second. 1 billion or 1,000,000,000 bits per second
Gigabit Ethernet 1000Mbps, 1 Billion bits per second over copper cabling
Half Duplex Single way transmission. Is capable of both Transmitting and Receiving but not simultaneously
Headroom The amount by which a network cable ACR exceeds 10dB above the specification.
Horizontal Cabling The structured cabling which connects the wall sockets to the network cabinet or wiring closet.
Hub The centre of a star wired network. May be passive or active in re-transmissions of network traffic.
Hz Frequency per second
IDC Insulation Displacement Connection. The connection is made by forcing the wire between two sharp blades which cut through the plastic insulation to contact with the copper conductor.
IEEE Institute of Electrical & Electronic Engineers
IEEE 802 The IEEE project number dealing with LAN technologies
IEEE 802.3 Physical cabling layer standards for Ethernet
IEEE 802.5 Physical cabling layer standards for Token Ring
Impedance Measurement of the opposition to the flow of electrons in a cable. The combination of Resistance, Capacitance & Inductance.
Infrastructure The collection of communication components (excluding active equipment) that together provide support for the distribution of information within a building or campus
Insertion Loss The attenuation of a signal as it passes through a connector
Intranet A large private company network often spanning many countries
IP Internet Protocol. Along with TCP is used to track and deliver data packets over a network
IPX Internet Packet Exchange. A Novell networking protocol
ISDN Integrated Digital Network Services. High speed data transfer over the PSN
ISO International Standards Organization.
ISP Internet Service Provider. The company who provides a connection to the internet.
Jabber A transceiver on an Ethernet network that has failed and is transmitting continuously and has "locked up" the network with it's incessant jabbering
LAN Local Area Network
Local Talk A slow form of LAN linked to AppleTalk network. Transmits at 230 Kbps
MAC Media Access Control.
MAN Metropolitan Area Networks, Spanning a Town or City.
MAU Multiple Access Unit. IBM terminology for a token ring hub.
Media The physical wire of fiber for the transmission of signals
Miss-Wire Where the single wires in a UTP cable have been attached to the connector in the wrong sequence.
Mode A single wave traveling in an optical fiber.
Modem A device which modulates & demodulate the signals between digital to analogue circuits.
Multi mode Fiber optic cable which supports the ropogsation of multiple wavelengths. Diameter of 50 to 100 microns with a stepped refractive index. Can use inexpensive LED ligh sources.
N Connector Connectors used for thick Ethernet 10Base-5 coax cable
NEXT Near End Cross Talk. The effect of one cable pairs signal on the adjacent pairs
NIC Network Interface Card
NIR NEXT to Insertion loss Ratio
Numerical Aperture The angle at which a fiber will gather light and propagate it down the core.
NVP Nominal Velocity of Propagation. The speed a signal will travel down an electrical cable measured as a percentage of the speed of light in a vacuum. Normally 70% - 75%
Nway Auto-negotiation to the highest common protocol involving network speeds and full or half duplex between network interfaces.
Octopus Converts a 25 way 'D' type to individual 2,4,6 or 8 pair sockets
OSI Open System Interconnection. The world wide reference for the networking protocol stack. The network rule book.
OTDR Optical Time Domain Reflect-o-meter. A device for finding breaks in fiber optic cables or measuring the length.
PABX Private Automatic Branch Exchange, A switchboard, (PBX)
Packet A string of bits containing command information, destination and source addresses and data
PAM5 A signaling protocol using 5 voltage levels to denote data bits. Used in 100Base-T2 and 1000Base-T networks
Patch Cable The cable connecting the network panel and the active switch or hub.
Patch panel An array of connectors in the network cabinet to allow circuit rearrangements by plugging in patch cords.
PCM Pulse Code Modulation. Sampling an analogue signal at a regular rate and converting each sample to a digital code.
Physical layer Layer one of the seven OSI layers. This layer is responsible for the transmission of signals between computers.
POP Point of Presence. The connection point to the internet
POTS Plain Old Telephone System
Premises cabling The complete cabling infrastructure for the transmission of voice, data and video throughout a given building.
Propagation delay The time for a signal to travel from input to the output of a device.
Protocol A data transfer mode using Bit codes, Start Stop bits, Parity. Both transmitter and receiver must use the same protocols.
PSELFEXT Power Sum Equal Level Far End Cross (X) Talk. Measures the summed cross talk from 3 pairs on the remaining pair having compensated for the known attenuation of the cable.
PSN Public Switched Networks. In short the telephone system.
PSNEXT Power Sum Near End Cross Talk. The effect on one pair of the summed crosstalk of the three other pairs.
Pulling tension The maximum pulling force which can be applied to a data cable without affecting it's electrical characteristics and consequently it's network performance.
Quartet Signaling Dividing a 100Mbps signal into four 25Mbps channels and transmitting them on all four pairs. Used by 100VG-AnyLAN and Cat3 UTP cabling
Reflection The return of electromagnetic energy that occurs when components are mismatched in network cabling. These reflections can cause data errors.
Repeater A device, usually a network hub or switch that receives and resends the data. The signal is thereby boosted and the wave reshaped allowing extended transmission distances.
Reversed Pairs The most common miss wire where the single wires in a pair have been reversed.
RFI Radio Frequency Interference.
RG 58 The specification of the coaxial cabled used for thin Ethjernet networks
Ring Network Describes a network in a complete ring. Now the fastest and most resilient network
RJ11 Registered Jack number 11. Small line plug and socket used on telephone handsets and modem connections.
RJ45 Registered Jack number 45. 8 pin plug and socket
RS232 Robust but outdated signaling protocol using 2 pairs.
RX Receive
SC Small Connector used for fiber optic terminations.
SC connector A connecter for terminating fiber optic cables. Can be snapped together to form a duplex connector for RX and TX transmissions.
SCSI Pronounced. Skuzzie. Small Computer Systems Interface. Connects peripherals to the computer mother board
Segment The area of a network that all node can see each other. Often called a collision domain
Shielded Cable with a braided or foil shield to keep out RFI and EMI.
Skew The differential delay between two adjacent cables carrying data transmitted simultaneously.
SNMP Simple Network Management Protocol. A protocol governing network management and device handling.
SOHO Small Office Home Office network system often mixing voice, data and video on the same cables.
Split Pairs Where the single wires from two different pairs have been swapped. If the same at both ends will not affect short cable transmissions, but will fail over longer distance. A common fault
ST connector Straight Tip. A connector registered to AT&T for fibre optic terminations
Star network All devices are attached to a central hub in a star configuration.
STP Shielded Twisted Pair copper cable
Structured cabling The fixed solid core cabling which makes up the building wiring.
Switch An Ethernet active repeater which reads MAC addresses and routes data to the individual node or network hub. Switches split up networks into smaller individual collision domains. A switch can route data at wire speed through all it's ports simultaneously.
TCP Transmission Control Protocol. Used with IP to track and deliver packets of data over a network.
TDR Time Domain Reflect-o-meter. A device for measuring the length of cables by "bouncing" a signal off the far end. The NVP must be known and programmed into the machine.
Terminator An electrical connector attached to the end of a cable to reduce signal reflections and unwanted noise.
TIA Telecommunication Industry Association
TIA 568A-4 The TIA Category 5E Specifications
Token Ring A network where a single token is passed around a network between computers. A computer must grab and hold onto the token before it can transmit. After transmission it releases the token back onto the network.
Topology Network architecture, circuit design and transmission protocols.
Transceiver An electronic circuit designer to transmit and receive data over a network. A NIC contains a transceiver as does a hub and a switch
Twisted Pair Pairs of 26 AWG wires twisted together the reduce RFI and Crosstalk.
TX Transmit
UN-balanced cable A single conductor carrying a single unbalanced signal, For example coax or thin Ethernet
USB Universal Serial Bus. A 12 Mbs connection port for games, printers, scanners and other PC peripherals
USOC Universal Service Ordering Codes Cabling system original used in the American telephone systems.
UTP Unshielded Twisted Pair. 4 twisted pairs in one sheath.
WAN Wide Area Network