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FAQ


The laymans guide to commonly used terms:

  1. ANSI (American National Standards Institute)
    The principle standards development body in the USA. ANSI is a nonprofit, non-governmental body supported by over 1000 trade organizations, professional societies, and companies. It is the USA’s member body to ISO.
  2. Architecture
    • Overall building wiring.
    • Local Area Network topology (bus, ring, star, etc.)
  3. Attenuation-to-Crosstalk Ratio (ACR)
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels.ACR is the calculated difference in dB between attenuation and crosstalk measurements. Please note that the ANSI/TIA/EIA-568-B.1 does not specify this test as a certification criteria, whereas the ISO/IEC 11801 Ed.2:2002 does require it. Once again, the higher the value in dB here, the better.
  4. ATM
    Asynchronous Transfer Mode. ATM is a high speed, (155 Mbps and over) cell relay, switching, and transport technology for either local or wide area environments.
  5. Attenuation
    Loss of signal strength as a function of distance. In optical fibre, it is the “dimming” of the light as it travels through the fibre expressed in decibels per unit feet (usually 1000 ft.)
  6. AUI
    Attached Unit Interface. Most commonly used with reference to the 15-pin D type connector and cables used to connect single and multiple channel equipment to an Ethernet transceiver.
  7. AWG
    American Wire Gauge. A standard for determining wire size. The gauge varies inversely with the actual wire diameter.
  8. Backbone
    The part of the network that carries the heaviest traffic. It is the main trunk cable from which all connections to the network are made.
  9. Backscattering
    The portion of light in a fibre that is redirected to that it travels in the opposite direction from the direction of intended transmission.
  10. Balun
    Balanced/Unbalanced. An impedance matching device to connect balanced twisted pair cabling with unbalanced coaxial cable.
  11. Bandwidth
    The data-carrying capacity of a transmission medium, usually measured in hertz, which equals cycles per second. (See Fibre Bandwidth)
  12. Baseband
    The frequency band occupied by a single or composite signal in its original or unmodulated form. Most common LAN transmission. Ethernet, Token Ring, and Arcnet use baseband transmission.
  13. BICSI
    A not-for-profit professional association for those involved in the design and installation of cabling infrastructures / telecommunications distribution systems. In 2004 BICSI celebrates 30 years of service to the industry. BICSI serves over 25 000 members in more than 90 countries around the world by providing high quality technical training and publications, conferences, professional registrations and other services. All BICSI training and material must be vendor neutral and standards based.
  14. Bluetooth
    A wireless technology that allows for signals to be transmitted over distances of <10 meters at a frequency of 2.4 Ghz at speeds of <1 Mbps.
  15. Bps
    Bits per second. Often preceded by K (kilo/thousands) or M (mega/million)
  16. Broadband
    A transmission facility that has a bandwidth (capacity) capable of carrying numerous voice, video and data channels simultaneously. Each channel operates on a different frequency. Cable TV is a broadband transmission.
  17. Buffer
    The material that surrounds the fibre cladding
  18. Bus
    A Local Area Network topology in which all workstations are connected to a single cable. On a bus network, all workstations hear all transmissions on the cable. Each workstation then selects those transmissions addressed to it based on address information contained in the transmission.
  19. CDDI
    Copper Distributed Data Interface. Another name for ANSI X3T9.5 Committee’s proposed 100 Mbps over UTP standard, TP-PMD (Twisted Pair Physical Media Dependent). CDDI is a trademark of Crescendo Communications/CISCO.
  20. Channel
    A physical or logical path for the transmission of information.
  21. Chromatic Dispersion
    The broadening of light pulses caused by the differing propagation speeds of various wavelengths that makes up the pulse (See Refractive Index).
  22. Cladding
    The transparent material, usually glass that surrounds the core of the optical fibre. Cladding glass has a lower refractive index than core glass.
  23. Closet
    Typically refers to the point on each floor of a building where the drop side device (workstation) connects to the system side equipment (LAN). Also often referred to as a cabinet.
  24. Connector (fibre)
    A device mounted on the end of a fibre for the purpose of mating the fibre to a source, receiver, or other device, or to another fibre through a coupling sleeve.
  25. Contention
    The condition when two or more stations attempt to use the same channel at the same time.
  26. Core
    The centre of an optical fibre. The core of communications grade fibre is made of glass that has a higher refractive index than the surrounding cladding glass. (See Cladding, Refractive Index).
  27. Cross Connect
    The physical connection between patch panels or punch down blocks that facilitates connection from the workstation to the host or network.
  28. Crosstalk
    The unwanted introduction of signals from one channel to another.
  29. Cross Wye
    A cable used at the host system, or network interface equipment, that changes pin/signal assignment in order to conform to a given wiring standard (USOC, AT&T PDS, DEC MMJ, etc.).
  30. Cut-Off Wavelength
    The shortest wavelength at which a single mode fibre will transmit only one mode.
  31. DCE
    Data Circuit-terminating Equipment. The designation given to equipment such as modems and multiplexers by the Electronic Industry of America (EIA). Differs from DTE (Data Terminal Equipment) in that it transmits data on pin 3 and receives data on pin 2.
  32. Decibel (dB)
    A logarithmic comparison of power levels, defined as ten times the base ten log of the ratio of input power to output power. One tenth of a bel.
  33. Delay Skew
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels. Delay skew is the differences in the propagation delay between the fastest and the slowest pairs in the same cable sheath.
  34. Dielectric
    Nonconductive. Fibre optic cables may be constructed using all dielectric materials. These cables are especially suitable for use in high EMI environments and areas of high electrical potential.
  35. DIN
    Deutsche Industrie Norm – The national standard for Germany.
  36. Dispersion
    The spreading, or broadening, of light pulses as they travel through the fibre. Dispersion is proportional to length (See Chromatic Dispersion).
  37. Distribution Frame
    See MDF and IDF.
  38. Drop
    Single channel attachment to the horizontal wiring grid (wall plate, coupling, MOD-MOD adapter).
  39. Drop Set
    All parts needed to complete connection from the drop (wall plate, coupling, MOD-MOD) to the terminal equipment. This typically includes a modular line cord and interface adapter.
  40. Drop Side
    Defines all cabling and connectors from the terminal equipment to the patch panel or punch down block designated for terminal equipment at the distribution frame.
  41. DTE
    Data Terminal Equipment. The RS232-C standard referring to equipment that transmits data on pin 2 and received data on pin 3. This standard typically applies to terminals, PCs, and printers.
  42. Dtype
    The standard connector used for RS232-C, RS423, and RS422 communication. It is most commonly used in 9, 15 and 25 pin configurations.
  43. Duplex
    Dual; Duplex fibre cables have two fibres.
  44. EIA 568A
    • Electronic Industries Association
    • A commercial building wiring standard for voice and data communications. First published July 1991.
  45. EMI
    Energy generated by outside sources, such as lighting systems and electric motors, which is received by copper data/voice cable and interferes with transmission.
  46. ESCON®
    Is a registered trademark of IBM Corporation.
  47. Equal Level Far-End Crosstalk (ELFEXT)
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels.ELFEXT is the Crosstalk measured on a disturbed pair at the opposite end from which the disturbing signal is transmitted, normalized by the attenuation contribution of the cable or cabling. The larger the value of ELFEXT loss in dB, the better the performance.
  48. Equal Level PowerSum Far-End Crosstalk (ELPSFEXT)
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels.ELPSFEXT combines the PSNEXT and ELFEXT tests i.e. one pair is energized and the measurement is taken from the other three adjacent pairs. The larger the value of ELPSFEXT loss in dB, the better the performance.
  49. Equipment cords
    These link equipment to the patching system.
  50. Far End Crosstalk (FEXT)
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels.FEXT is the amount of NEXT transmitted down the length of cable. This typically occurs on short lengths of cable, generally anything less than 15 metres. The NEXT is reflected down the cable to the far end, and any noise transmitted back down the cable will “attach” itself to the FEXT and push up the noise level. A see-saw effect is created with the noise just getting higher and higher until total communication breakdown. The user sees this as a gradual slowing down in network response times.Design tip: Try to ensure that the fileserver is installed outside of this 15 metre danger zone. This is generally the busiest machine on the network and too much noise on these short links can generate server crashes. (See Return Loss testing too).
  51. FDDI
    Fibre Distributed Data Interface. A standard for a 100 megabit-per-second local area network.
  52. Feeder Cable
    25-Pair cable run from the equipment location to the distribution frame. Equipment end is typically wired with a female 50-position connector and the distribution frame end is wired with a male 50-position plug.
  53. Ferrule
    The alignment sleeve portion of an optical connector.
  54. Fibre bandwidth
    Simply, the lowest frequency at which the fibre loss does not increase beyond 3 dB compared to the zero frequency output. Specifically, the lowest frequency at which the magnitude of the fibre transfers function decreases to a specified fraction of the zero frequency value. The fibre bandwidth is expressed as a function of distance, typically in MHz-km. It is a measure of the information carrying capacity of the fibre.
  55. FRD
    Fire retardant. A rating used for cable with Teflon or equivalent jacket and insulation. Use this cable when local fire codes call for low flame and low smoke, or when cable is run through a forced air plenum.
  56. Gigabit Ethernet
    Gigabit Ethernet provides the capacity for server interconnection, campus backbone architecture and the next generation of super user workstations with a seamless upgrade path from existing Ethernet implementations.
  57. Graded Index Fibre
    A fibre in which the core has a refractive index that decreases as a function of the radial distance from the center of the core. Graded indexing is used in multimode fibres to minimize the effects of modal dispersion (See Refractive Index).
  58. GRP
    Glass reinforced plastic.
  59. Harmonica
    A device that is attached to the end of a connectorised feeder cable that converts the 25 pair into individual 4, 6 or 8 wire modular channels.
  60. Home Run
    A cable run usually consisting of two, three, or four pair cable from a wall plate in a fixed wall office, to a termination point at the distribution frame.
  61. Horizontal
    That portion of the system cabling that is attached to, or “fed” from a common distribution point.
  62. IDC
    Insulation Displacement Contact. A type of wire terminating connection in which the insulating jacket is cut by the connector when the wire is inserted.
  63. IDF
    Intermediate Distribution Frame. An intermediate cross connect point, usually located in a wiring or utility closet. A trunk cable or LAN backbone is run rom each IDF to the MDF (Main Distribution Frame). Also referred to as SDF (Sub-Distribution Frame).
  64. IEEE
    Institute of Electrical and Electronic Engineers. An international professional society that issues its own standards and is a member of ANSI and ISO.
  65. IEEE 802.3
    Is a physical layer standard for 10BASE-T, Ethernet, and Starlan.
  66. IEEE 802.5
    Is a physical layer standard for Token Ring.
  67. IEEE 802.12
    Is a physical layer standard for 100 VG.
  68. Infrared laser
    Also referred to as free space laser, allows for transmission speeds of up to 155 Mbps between distances of up to 6 km apart.
  69. Insertion Loss
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels. Formerly known as attenuation, insertion loss is a measurement of the loss of signal over a length of cable. Whilst you will seldom get a fail condition here, it is important to note that a factor that could influence IL is excessive heat – watch out for cable runs in ceilings close to the external roof or anywhere near heat emitting devices. For Insertion Loss, the smaller the loss in decibel (dB), the better the performance.
  70. ISDN
    Integrated Services Digital Network.
  71. ISO
    International Standards Organisation.
  72. Jacket
    The outside covering of a cable. Not part of the fibre or the fibre buffer.
  73. Jitter
    The time-varying difference between the phase of a recovered clock and the phase of the source clock.
  74. Accumulated Jitter
    The total growth in phase difference as a signal passes through many circuits, for example, the total jitter in an entire token ring.
  75. Correlated Jitter
    The phase differential that is directly related to the different frequencies in the data pattern. This appears as a “Bit spread” and can cause overlapping of neighbouring pulses, resulting in intersymbol interference.
  76. Transferred Jitter
    The phase variance which is propagated through a circuit as compared with an arbitrary base or originating signal.
  77. Uncorrelated Jitter
    The portion of the phase differential that is independent of the data pattern, generally caused by EMI or channel-generated noise.
  78. Kevlar
    An aramid fibre used to provide crush resistance and pulling strength in a fibre cable. Kevlar is a trademark of the Du Pont Company.
  79. LAN
    Local Area Network. A data communications network spanning a limited area. It provides communication between three or more computers and peripherals, in most cases using a high speed media as its backbone.
  80. LED
    Light Emitting Diode.
  81. Length
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels. For Permanent Link tests, the length should not exceed 90 metres, and for Channel tests the length should not exceed 100 metres. Before testing a site, an important factor to remember is that you have to set up the NVP for the cable. The NVP, or Nominal Velocity of Propagation is a value that the tester uses in its calculation of the cable length. A signal is sent down the length of cable and the measured time (propagation delay) is then multiplied by the NVP value to determine the length of cable. The NVP value is unique to each cable manufacturer, and you should check with them what the value is for their cable. The default NVP on most testers is 72%, but most of the locally produced cable differs from this, so please check it first.
  82. LID
    Local Injection/Detection. Device used for aligning fibres during splicing.
  83. Line Cord
    The connecting cord between the terminal device and the drop.
  84. LJLP
    Line Jack Low Profile
  85. Loose Tube
    A protective tube surrounding one or more fibres, usually in cables designed for use in outside plant applications. Sometimes called loose buffers.
  86. Low Smoke Zero Halogen (LSZH)
    Fire retardant cable
  87. Margin
    The allowance for additional attenuation in a system design above what is necessary for system operation. Margin gives room for additional splices in the event of a cable break and allowance for the degradation of the transmitter with age, and so on.
  88. MAU
    Multi Station Access Unit. A wiring concentrator used to form a star-wired ring configuration.
  89. Mbps (Mb/s)
    Megabits per second
  90. MDF
    Main Distribution Frame. The central connecting point for both voice and data wiring. Also serves as the main location from which cross connecting and testing are done.
  91. Mechanical Splice
    One of several available devices for splicing fibres in lieu of fusion splicing. Not to be confused with connectors. (Connectors are primarily designed for indoor use in applications where easy re-connection is required. Mechanical splices are primarily designed for any environment where a permanent, low loss joint is required).
  92. Microbending
    Bends in the fibre, usually of a radius less than 1mm, that cause a localized increase in the loss of the fibre due to the “leaking” of light through the core-cladding interface.
  93. MMJ
    Modified Modular Jack. A six-wire modular jack with the locking tab shifted off to the right side. Used in the DEC wiring system.
  94. Mode
    Specifically, an electromagnetic field distribution that satisfies theoretical requirements for propagation in a waveguide or oscillation in a cavity. Modes exist in fibres and lasers. Very simply, they may be thought of as “paths” in which the light rays travel. (Note: Modes are not to be confused with channels).
  95. Multimode (MM)
    A device that emits or a fibre that carries multiple modes of light.
  96. Nanometer (nm)
    A unit of measure equal to 10 -9 (one billionth) meter. Used to measure the wavelength of light.
  97. Near End Crosstalk (NEXT)
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels.NEXT is the measurement of noise that is electrically induced from one pair in the cable onto another pair, or pairs. If this noise becomes excessive, it will lead to signal loss or even total disruption of communication. There are many reasons for NEXT failures, but the most important thing to look out for is to keep the pair twists as tight as possible up to the point of termination. Also, do not remove more cable sheath than is necessary to do the termination. When testing, the larger the value of NEXT loss in dB, the better the performance.
  98. Network Interface
    The physical point where the building or equipment wiring interconnects with the Local Exchange Carriers.
  99. Numerical Aperture (NA)
    Simply, a non-dimensional number that indicates the ability of a fibre or other device to receive light input. Specifically, the sine of the half angle of the acceptance or radiance cone of an optical fibre, multiplied by the refractive index of the material in contact with the fibre face.
  100. Octopus
    A device that is attached to the end of a connectorised feeder cable that converts the 25-pair to individual 2, 4, 6 and 8 wire channels.
  101. OM1, OM2, OM3
    Naming conventions for Multimode fibre optic transmission where distance limitations are 33, 82 and 300 meters respectively for a transmission speed of 10 Gbps. Frequency – 200 / 500 Mhz / km, 500 / 500 Mhz / km and 1 500 / 5 Mhz / km respectively.
  102. Optical Time Domain Reflectometer (OTDR)
    An instrument that allows the characterization of a fibre by the analysis of backscattered light. The OTDR is one of the most useful diagnostic tools in the fibre trade.
  103. OS1
    Naming convention for Single Mode fibre optic transmission where distance limitations are between 5 – 40 km, frequency at 1 000 Ghz and transmission speeds reach beyond 10 Gbps.
  104. Patch cords
    Used to connect between patching systems which could either be cross connect blocks or patch panels.
  105. PC
    In fibre connectors, an acronym for “Physically Contacting”. PC type connectors are designed to bring two mated fibres into actual contact in an effort to minimize loss and reflections.
  106. Physical Layer
    Level 0 (the lowest layer) in the OSI architecture. Concerns itself with the voltage levels, cabling, speed, and signaling used between equipment.
  107. Polarisation
    The modular connector mechanical form factor.
  108. PowerSum Near End Crosstalk (PSNEXT)
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels.The NEXT test is a measurement of noise between pairs i.e. a signal gets sent down one pair and the tester “listens” for noise on the adjacent pairs, one at a time. With the PSNEXT test, a signal is still sent down one pair, but now the tester “listens” for noise on all the adjacent pairs simultaneously. PSNEXT is a requirement for applications that communicate over multiple pairs at the same time, such as Gigabit Ethernet.
  109. Premises Wiring
    Also commonly referred to as Premises Cabling. The technology of wiring buildings and property for data, telephone, video, and other electrical/electronic functions.
  110. P.D.S.
    Premises Distribution System.
  111. Propagation Delay
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels. Propagation delay measures the time taken for the signal to travel from the transmitter to the receiver.
  112. Pulse Dispersion
    The spreading of light pulses as they travel in an optical fibre. See Chromatic Dispersion.
  113. PVC
    Polyvinyl Chloride. The material most commonly used for the insulation and jacketing of cable.
  114. RCDD
    BICSI’s best known registration is the RCDD – Registered Communications Distribution Designer. RCDD’s must demonstrate proficiency in the design, integration and implementation of telecommunications transport systems and related infrastructure components. RCDD’s are tested on the contents of BICSI’s world renowned TDMM – Telecommunications Distribution Methods Manual. Currently there are more than 7000 RCDD’s around the world.The RCDD qualification is internationally recognised.
  115. Refractive Index (IR)
    Index of Refraction. The relative “density” of a transmissive material as a comparison of the speed of light in the material in question to the speed of light in free space.
  116. Return Loss
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels. Return loss is a measurement of the power reflected from the cabling in dB. Return loss is basically the measurement of the impedance mismatches caused when components such as patch panels, wall outlets or consolidation points “break” the cable run. Excessive pulling, twisting or kinking of cables i.e. altering the cable’s construction can contribute to return loss failures. The larger the value of return loss in dB, the better the performance.
  117. RJ
    Registered Jack
  118. RJLP
    Registered Jack Low Profile
  119. RJSE
    Registered Jack Side Entry
  120. Ring
    • A Local Area Network Topology in which data is sent from workstations via a loop or ring.
    • One conductor of a pair (vs. tip)
  121. SDF
    Sub Distribution Frame. (See IDF.)
  122. SC
    A type of optical fibre connector. The SC utilizes the same 2.5mm ferrule as the ST, held in a housing that allows for “push-pull” insertion and removal of the connector from the adapter. Rapidly becoming the connector of choice for data networks.
  123. Simplex
    Single; Simplex fibre cables house only one fibre.
  124. Singlemode (SM)
    A device that emits or a fibre that carries a single mode of light.
  125. SMA
    A type of fibre optic connector, used extensively in telephone installations before the introduction of the ST-type connector. No longer popular. Originally an acronym for “Sub-Miniature Assembly”.
  126. Splice
    A permanent joint, joining two optical fibres.
  127. ST®
    A registered trademark of Lucent Technologies for their fibre optic connector. Originally, an acronym for “Straight Tip”.
  128. STII®
    A registered trademark of Lucent Technologies for their fibre optic connector.
  129. Star
    A Local Area Network topology in which all workstations are wired directly to a central workstation or hub that establishes, maintains, and breaks connection to the workstations.
  130. System Connect
    The method by which connection is physically made to the host computer or Local Area Network.
  131. System Side
    Defines all cabling and connectors from the host computer or Local Area Network to the cross connect field at the Distribution Frame.
  132. 10BASE-T
    10 Mbps 802.3/Ethernet over standard unshielded twisted-pair cable specification. 10BASE-T supports network configurations using the CSMA/CD access method over a twisted pair transmission system up to 100m in length without the use of a repeater.
  133. Tight Buffer
    A buffer, or coating, that is extruded directly over the primary fibre coating. Tight buffers are common in fibre jumpers and patch cords.
  134. TP-PMD
    Twisted Pair Physical Media Dependent. ANSI X3T9.5. Committee’s proposed 100 Mbps over UTP standard. Also referred to as CDDI (Copper Distributed Data Interface).
  135. Topology
    The architecture of a network, or the way circuits are connected to link the network nodes together.
  136. Transceiver
    A device used in contention networks for sending data over the network and receiving data from the network.
  137. Trunk Cable
    Trunk Cable Typically refers to a copper twisted pair backbone or vertical riser cable consisting of multiple groups of 25 pairs.
  138. USOC
    • Uniform Service Ordering Code
    • A term originally used by the telephone company to specify installation of a standard modular jack other than RJ11W or RJ11C. More recently refers to a modular standard (tip/ring sequence).
  139. UTP
    Unshielded Twisted Pair. Twisted pair cable without either individual or overall shielding.
  140. Vertical
    That part of a wiring grid that connects the host computer or Main Distribution Frame to equipment located on other floors.
  141. Voice over IP (VoIP)
    VoIP works through sending voice information in digital form in packets, rather than in the traditional circuit-committed protocols of the public switched telephone network.
  142. Wavelength (l)
    The distance an electromagnetic wave travels during the time it takes to oscillate through one complete cycle. The wavelengths of light used in fibre communications are usually measured in nanometers (nm). The common wavelengths or “windows”, are 850nm, 1300nm and 1550nm.
  143. Wavelength Division Multiplexing (WDM)
    The multiplexing of signals by transmitting them at different wavelengths along the same fibre.
  144. Wiremap
    One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels. The wiremap test checks the way in which the cable is terminated. There are 4 pairs, or 8 wires in a cable and each one can only go into one dedicated position. Anyone that has terminated a patch panel in a room with bad lighting can tell you that it is quite possible to make a mistake. If the wiring is incorrect, the tester will stop testing at this point and you will have to carry out the necessary repairs.
  145. Work Area Cords
    Cords that are used at the work area. In S.A. these were commonly referred to as fly leads.
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