Understanding IT Terminology

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 light 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 Ethernet 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

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