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Glossary of IT 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
1000Base-T - 1000Mbps, four pairs of cable running at 250Mbps per pair.
100Base-T2 - 100 Mbps Ethernet running baseband on two pairs
100Base-T4 - Four pairs of Cat3 or better cable. Transmits at 25 Mbps on all four pairs.
100Base-TX - 100 Mbps Ethernet running baseband . Full duplex
10Base-2 - Thin Ethernet, segment length 185 metres, max 5 segments connected by repeater
10Base-5 - Thick Ethernet,segment length 500 metres, max 5 segments connected by repeater
10Base-T - 10 Mbps Ethernet using twisted pair copper cable - baseband
ADSL - Asymmetric Digital Subscriber Line.
ANSI - American National Standards Institute.
ASCII - American Standard Code for Information Interchange. Originally a 7 bit code later 8 bit for communication interfaces.
Attenuation - Loss of signal amplitude due to absorbtion in any transmission medium
Bandwidth - The capacity of a medium to a signal
Baseband - The full bandwidth of the medium is used to transmit an unmodulated signal
BAUD - Number of signal or voltage transitions per second. Not the same as Bits Per Second.
BNC - Bayonet connector used with thin Ethernet cables
bps - Bits per second
Broadband - The bandwidth of the cable is divided into channels. Each channel is seperated by a guard band. The data signal is used to modulate the channel frequency.
Broadcast - To send data to more than one device at a time. A network broadcast will cover an entire Level 2 network but generally cannot be routed.
Bus Network - A network with all devices sharing one common cable. E.g Thick and Thin Ethernet
CAT1 - Unshielded Twisted Pair for use as speaker or door bell wire.
CAT2 - UTP 1.5Mhz, analogue telephone applications.
CAT3 - UTP 16Mhz.
CAT4 - UTP up to 20Mbs
CAT5 - UTP cable, data rate 100Mbps
CAT5E - Enhanced Cat 5 data cabling with more stringent tests and headroom. Still 100Mhz
CAT6 - cabling standard designed to support up to 250 Mhz over UTP.
CAT7 - cabling standard still under development designed to support up to 600 Mhz over UTP.
Coax - Coaxial cable with a copper inner conductor and a copper braid and/or foil screen. Used in a wide variety of situations
Collision domain - All the nodes on an Ethernet segment that are affected by data collisions. Switches and bridges and hubs break up a network into individual collision domains
Crosstalk - interference picked up from an adjacent wire pair within the same cable
CSMA/CD - Carrier Sense Multiple Access with Collision Detect.
D Type - D Shaped connector with an array of pins in 9, 15 and 25
DDR memory. Double Data Rate SDRAM. Maybe shown as DDR-400 or PC3200.
EMI -Electro Magnetic Interference. Unwanted noise from a source such as fluorescent lighting and electric motors and other electric or electronic equipment.
Ethernet - A LAN protocol using CSMA/CD
Fast Ethernet -100Mbps CSMA/CD Ethernet
Full duplex - Allows data transmissions in both directions simultaneously
Gigabit Ethernet - 1000Mbps, over copper cabling
Giga - decimal multipier, value 1,000,000,000
Half Duplex - Two way communication but only one at a time
Hub - The repeater that forms the centre of a star wired network.
Hz - Frequency , cycles per second
IDC - Insulation Displacement Connection. Quick and easy way to terminate ribbon or other cable. Each conductor is forced between two small metal edges so the the insulation
Impedance - The combined effect of Resistance, Capacitive Reactance & Inductive Reactance in a circuit is cut and the blades contact the conductor.
IP - Internet Protocol.
IPP - Internet Presence Provider
IPX - Internet Packet Exchange. Novell's older protocol
ISDN - Integrated Digital Network Services.
ISO - International Standards Organisation.
ISP - Internet Service Provider.
Jabber - A condition where a transmitter has failed and is continuously transmitting and causing problems on the local network segment.
KILO - decimal multiplier - value 1000
MAN -Metropolitan Area Networks
Media - The physical wire, fibre or other medium for transmission of signals
Mega - decimal multipier, value 1,000,000
Modem - Modulator-Demodulator,
NEXT - Near End Cross Talk. Crosstalk measured at the nearest end of the cable
NIC - Network Interface Card
NIR - Ratio of NEXT to Insertion loss
NVP - Nominal Velocity of Propagation. The speed a signal travels along a cable. Normally 66% - 75% of speed of light in vacuo
OSI - Open System Interconnection. Anyone who has ever been on a networking course will have come across the OSI from the ISO
OTDR - Optical Time Domain Reflectometer. Same idea as a TDR but uses a light pulse rather than electrical.
PABX - Private Automatic Branch Exchange.
Packet - An assebly of data bits containing command information, destination and source addresses and data, flags and protocol information.
Paperless Office - A computing ideal - about as useful as a paperless loo.
Patch Cable - The cable used to connect a network patch panel port to a switch port.
Patch panel - Termination port for a bundle of cables from floor and wall ports, or a PABX
PICNIC - user error - Problem In Chair Not In Computer
PSTN - Public Switched Telephone Network.
Reflection - A signal transmitted on a cable will reflect back to the transmitter should any anomaly exist in that cable. The greatest reflections are caused by either open-circuit or short-circuit conditions. Smaller reflections are caused by kinks or crush points. A TDR can detect these faults by measuring the reflection and the time taken to return and return a distance to fault reading.
Repeater - A device, usually a network hub, receives and resends all data. The signal is amplified to extend the network range.
Reversed Pairs - A wiring fault where the single wires in a pair have been reversed.
RFI - Radio Frequency Interference.
RG 58 - Coaxial cable used in thin Ethernet networks (10Base2)
RJ11 - American telephone jack. Also used elsewhere for telephone connections 6 pins positions, 2, 4 or 6 conductors used.
RJ45 - 8 pin plug and socket used in data comms, 2 standard connections methods, but other propriatory arrangements exist.
RS232 - Serial communications standard
RX - Receive
SCSI - Small Computer Systems Interface. Data transfer rates anything from 4MBytes to 160MBytes per second. Parallel and serial variants exist.
SDRAM - Synchronous Dynamic Random Access Memory.
Segment - The part of a network that all nodes can see each other. Also a collision domain.
Shielded - Cable with a braided or foil shield to keep out RFI and EMI.
SNMP - Simple Network Management Protocol.
Split Pairs - A wiring fault. Where the single wires from two different pairs have been swapped.
Star network - All devices are attached to a central hub in a star configuration.
STP - Shielded Twisted Pair
Structured cabling - Cabling and associated equipment that forms the network in a building.
Switch - A level 2 device that communicates with Ethernet devices using the MAC address
TCP - Transmission Control Protocol.
TDR - Time Domain Reflectometer. A device for measuring the length of cables or distance to a fault by transmitting a signal and timing the return signal from the far end. The Nominal Velocity of Propagation for the cable under test 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. Used on SCSI and 10Base2 cables, amongst others.
TIA - Telecommunication Industry Association
Topology - Network architecture, circuit design and transmission protocols.
Twisted Pair - Pairs of wires twisted together the reduce RFI and Crosstalk.
User Intervention - an invitation from a printer to screw things up a bit more.
UTP - Unshielded Twisted Pair. 4 pairs of wire, each pair twisted round its partner.
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