| Glossary
66-Type Punch-Down Block
A block consisting of four columns of 50 pins each, onto which
the 50 wires of the 25-pair group are placed. Each wire is placed
in a pin, and then punched into place, stripping the insulation
in the process. The pins in columns 1 and 2 are shorted together,
and the pins in columns 3 and 4 are shorted together. This creates
an input and output side of the block.
To connect the two halves, bridging or shorting
clips are used between pins 2 and 3 of any particular row. The
66-Type Punch-Down Block provides easy access to each wire and
is used to terminate most twisted-pair cable. Most installed 66-Type
Blocks do not support Category 5.
802.3
The Institute of Electrical and Electronic Engineers (IEEE) physical
layer standard for Ethernet coaxial cable. It specifies the carrier
sense multiple accesses with collision detection (CSMA/CD) access
method on bus topologies.
802.5
An IEEE standard for token ring networks that provides for a ring
topology configuration (a closed set of active taps connected
by point-to-point links). Access to the ring is granted when a
token is received and passed in a logical (and physical) ring
sequence between the workstations.
10BASE-T
A twisted-pair Ethernet cable standard that conforms to IEEE 802.3
specifications and can carry data at 10 Mbps.
Alternating Current (AC)
An electric current whose direction is periodically reversed.
This is the common form of electricity generated in homes and
offices. All electronic digital systems use direct current (DC)
in their circuits and have built-in power supplies to convert
the AC into DC.
ANSI
American National Standards Institute.
ARCNET
An acronym for Attached Resource Computer Network, a token-passing
bus architecture network developed by Datapoint Corporation.
ARCNET, the first local area network technology,
has a flexible architecture that allows both star and bus topology
networks, or a combination that can be described as a distributed
star with branches. ARCNET can use single twisted-pair, coax and
duplex fiber optic cabling.
Attenuation
The decreasing of a transmitted signal as it travels along a cable.
The longer the cable the more loss there will be. Above a certain
amount of loss, the cabling may not transmit network data reliably.
Attenuation to Crosstalk Ratio (ACR)
An indication of how much larger the received signal of a pair
is compared to the noise (NEXT) on the same pair.
Bandwidth
Maximum information carrying capacity of a channel.
Basic Link
A basic link is a model defined by TSB-67. A basic link is similar
to what an installer might work with - including the wall plate,
horizontal wiring and first cross connection. It is intended to
be used by system designers and users of data telecommunications
systems to verify the performance of permanently installed cabling.
A basic link consists of up to 90 meters of horizontal
cabling, a connection at each end, up to 2 meters of test equipment
cord from the main unit of the field tester to the local connection,
and up to 2 meters of test equipment cord from the remote connection
to the remote unit of the field tester.
CENELEC
Comite Europeen de Normalization Electrotechnique
Certification
An automated test process that verifies that test results meet
established standards requirements.
Channel
All elements of the communications link connecting a DTE (typically
a PC or server) to a hub in the wiring closet. Includes fiber
cabling, patch cords, connections, and splices if any. A channel
is a model defined by TSB-67.
It is similar to what a user works with to transmit
information between a personal computer and its hub, or concentrator.
A channel includes up to 90 meters of horizontal
cable, a work area equipment cord, a telecommunications outlet/connector,
an optional transition connection close to the work area, and
two cross-connect connections in the telecommunications closet.
According to the TSB-67, the total length of equipment
cords, patch cords and jumpers shall not exceed 10 meters. It
is important to note that the connections to the equipment at
each end of the channel are not included in the channel definition.
Cladding
A protective layer made of glass or plastic, which surrounds the
core. The cladding has a lower index of refraction than the core,
which helps keep light in the core.
Core
The center of a fiber optic cable usually made of extremely clear
glass or plastic, through which the light travels.
Electronic Industries Association (EIA)
An organization of manufacturers of electronic parts and systems.
The EIA sets such standards as the EIA-232 interface specification.
Electromagnetic Interference
An unwanted signal that enters the transmission line from fluorescent
lights, fan motors, etc. See also RF Interference.
ELFEXT
Equal Level Far End Crosstalk. This is far end crosstalk adjusted
for attenuation. It can be thought of as far end ACR.
FDDI
Fiber Data Distributed Interface
Hertz (Hz)
The frequency of electrical vibrations (cycles) per second. One
Hz equals one cycle per second.
IDC-Type Punch-Down Block
A twisted-pair wiring panel in which each wire is placed in a
pin, and then punched into place, stripping the insulation in
the process.
IEC
International Electro-technical Commission Institute of Electrical
and Electronic Engineers (IEEE). A membership organization, including
engineers, scientists and students in electronics and allied fields,
that is involved with setting standards for the computer and communications
field.
Impedance
The resistance to the flow of alternating current in a circuit.
ISO
International Standards Organization
Local Area Network (LAN)
A communications network serving multiple users within a confined
geographical area (as in the same building or group of adjacent
buildings).
It usually refers to the interconnection of personal
computers. Shared data is stored in a high performance PC called
a fileserver, which serves as a remote disk drive to all network
users. Users may also share printers, modems and other peripheral
devices.
Loopback
The shorting together of wires in a connector so that a signal
sent along the wire returns to its place of origin.
Megahertz (MHz)
One million cycles per second. See Hertz (Hz).
Micron
1 millionth of a meter
Multimedia network
A network that allows access to Integrated Voice and Data (IVD)
over standard unshielded telephone twisted-pair wiring. Multimedia
LANs use existing wiring to carry both voice and medium-to-high
speed data in typical office environments.
Multimode
Fiber optic cabling with a wider core (typically 50 or 62.5 microns)
that allows light to travel in multiple paths, such that it is
reflected back from the cladding back into the core as it travels
down the core.
Near End Crosstalk (NEXT)
The interference measured on a wire adjacent to the wire on which
the signal is being sent. Near end crosstalk measurements show
the amount of signal leaking when measured close to the signal
generation point.
If the crosstalk coupling across at the near end
is great enough, it can interfere with signals coming from a remote
point, which are diminishing as they reach the same spot.
Noise
Any extraneous signal that invades the transmission of electrical
pulses or frequencies along a cable. Noise is measured as impulse
or Root-Mean-Square (RMS).
Nominal Velocity of Propagation (NVP)
The speed of data transmission along a cable relative to the speed
of light in a vacuum.
OLB
Optical Link Budget
OTDR
Optical Time Domain Reflectometer. A sophisticated fiber test
tool that locates fiber breaks, and can determine loss per connection,
splice, or segment.
Patch cable (Test Cable)
A short, flexible cable terminated at both ends that are used
to interconnect LAN equipment.
Pin
One of the male leads on a multiple line plug, such as an RJ-45
connector or an EIA-232 connector.
Plenum cable
Cable certified to be fire resistant and to produce a minimum
of smoke. It can be installed in the space between the false ceiling
and the floor or ceiling above, called the plenum.
Punch-Down Block
A central termination point for twisted-pair cable. Each wire
is placed in a pin, and then punched into place, stripping the
insulation in the process. See also 66-Type Punch-Down Block and
IDC- Type Punch-Down Block.
Resistance
A property of a conductor, which resists or opposes the flow of
current in an electronic circuit.
Return Loss
This is a measure of the overall uniformity of a link's impedance
relative to 100 ohms.
RF Interference
An unwanted signal that enters the transmission line from radio
and television transmitters. With this type of interference, the
cable acts as an antenna. See also Electromagnetic Interference
and Noise.
Screened Twisted-Pair (ScTP) cable
Four pair UTP, with a single foil or braided screen surrounding
all four pairs in order to minimize EMI radiation or susceptibility.
Screened twisted pair is sometimes called Foil Twisted Pair (FTP).
Screened/Shielded Twisted Pair (SSTP)
Four pair cabling, with each pair having its own individual shield,
in addition to an overall shield surrounding all four pairs. SSTP
offers similar performance to Type 1 STP except with 4 pairs (rather
than 2) and in a 100-ohm impedance (rather than 150).
Shield
An insulating material used with coax or twisted-pair cable to
reduce electrical interference.
Shielded Twisted Pair (STP)
Two pair cabling, with both pairs having its own individual shield,
in addition to an overall shield surrounding both pairs. STP is
most familiar to LAN users as the heavy black IBM Type 1 cabling
found in token ring networks.
Single-mode
Fiber optic cabling with a narrow core (8-9 microns) that only
allows light to travel in one path (i.e. one mode).
Time Domain NEXT (TDNXTSM)
A totally new concept in cable troubleshooting offers unique advantages:
- True NEXT vs. length pinpoints causes of NEXT
failures can clearly and accurately identify whether connectors
or cable are the cause of the failure.
- Magnitude scaling (Cat 5, 5E, 6) auto-adjusts
for relative NEXT of different category links.
- When used with S-Band Technology (patent pending),
creates foolproof diagnostic capability.
Time Domain Return Loss (TDRLSM)
Measures return loss versus length and delivers benefits:
- True return loss versus length identifies sources
of RL patent pending S-Band technology for precision faultfinding.
- Can easily tell if connections meet Cat 5, Cat
5E, Cat 6, or Cat 7 requirements
TIA
Telecommunications Industry Association
Time Domain Reflectometry (TDR)
A diagnostic technology in which a pulse of known amplitude and
duration is sent along a cable. When an open or short is detected,
a pulse reflects back to the device generating the signal.
The device then measures how long the round trip
took and converts this to distance using the cable's NVP.
Token Ring Network
A physical ring network topology. On a token ring network, data
moves around the entire ring, from one workstation to the next,
eventually receiving the transmitted information back after it
completes one round trip around the ring.
The token, a specific bit sequence that circulates
around the nodes, gives permission to transmit.
Twisted-Pair cable
Cable in which two wires are wrapped (or twisted) around each
other between two and 12 times per foot of length. Most twisted-pair
cabling contains either four or 25 pairs of wires.
Unshielded Twisted-Pair (UTP) cable A common type
of twisted-pair cable that does not have a shield wrapped around
the wires.
Wire closet
An area in a building in which punch-down blocks are centralized;
a central termination area for network or telephone cabling.
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