- Cabling Jargon
The
key to understanding any technology is understanding the language of
the technology – the jargon. This page is an overview of cabling jargon
to introduce you to the language of the technology and help you
understand what you will be reading in this section. We suggest you
read this section carefully to help your understanding of the rest of
the pages and refer back to it when you encounter a term that you do
not recognize.
What is Premises Cabling?
By
premises cabling, we mean the cabling used inside buildings (and in
restricted geographic areas like campuses or among business facilities)
that follows industry standards. Mostly we are refering to structured
cabling systems defined by TIA-568 or ISO/IEC 11801 and related
standards that are used
for LANs, telephone systems and even other systems adapted to
structured cabling like CCTV, security or building management. Other
systems that depend on cabling such as security and building control
are migrating to structured cabing for its widespread availability and
predictability.
Here's an overview of
the basic jargon used in cabling.
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- To begin with, what do we
call this technology of cabling?
People call it lots of things:
VDV (for voice/data/video) cabling
Premises (e.g. indoor) cabling
Structured cabling (from the standards)
Data/voice cabling
Low voltage cabling (less than power cables)
Limited energy
cabling (mostly harmless)
Teledata
cabling (a made-up word from telecommunications and data)
Datacom cabling (an abbreviated version of data communications)- ....but most people call it"premises cabling" for its application or "structured
cabling" after the "568" standard.
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- Premises cabling is the infrastructure for
telephone and LAN connections in most commercial installations
and even in some modern homes. It's also used for fire alarms,
building management, audio and video.
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- Structured Cabling is the standardized achitecture and components for communications cabling
specified by the EIA/TIA TR42 committee and used as a voluntary
standard by manufacturers to insure interoperability.
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- Cabling Standards
- Structured cabling is based
on a number of industry standards - voluntary interoperability standards - developed
by manufacturers who want their products to work
together. They meet in committees several times a year and decide
on the specifications of their products. These common specs mean
that equipment will work on any cabling system that follows the
standards and most cabling components can be interchanged without
adversely affecting performance.
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- EIA/TIA:
In the US, Electronics Industry Alliance/Telecommunications Industry
Association (TIA), an industry trade association that creates voluntary
interoperability standards for the products made by member companies.
Worldwide standards rely on ISO and IEC standards. More.
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- EIA/TIA 568:
The main standard document for structured cabling, usually referred to
as simply "568." It is now on the "C" revision, published in 2009.
Worldwide, ISO/IEC 11801 is approximately the same as TIA-568. More.
EIA/TIA 569: Covers pathways and spaces. Defines the "telecom
closet" or telecom room as it is now called. (ISO/IEC 14763-2)
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- EIA/TIA 570: For residential cabling.
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- EIA/TIA 606: cabling system administration (documentation) (ISO/IEC 14763-1)
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- EIA/TIA 607: Grounding and bonding
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- Standards are not code!
They are voluntary
interoperability specifications. However every installation must
be compliant to local building codes for safety!
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- NEC (National Electrical
Code): written by NFPA
(National Fire Protection Assn.) this code sets standards for
fire protection for construction and is a legal requirement in
most cities.
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- Structured Cabling Architecture
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Structured Cabling Terms:
The terms listed her are the traditional terms used since the beginning of structured cabling, but a new set of terminology is being introduced.-
- Telecom Closet (TC): The location of the connection between
horizontal cabling to the backbone. Now often called "Telecom
Room" to imply it's usually bigger than a closet!
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- Main Cross-Connect (MXC): The old telco term for the location
of the main electronics in a building. LAN people may call it
the equipment room
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- Intermediate Cross-Connect
(IXC) : A room in between
the TC and MXC where cables are terminated
(TIA has proposed to change these terms in future standards. Here are the new terms.)-
- Work Area Outlet: The jack on the wall which is connected
to the desktop computer by a patchcord
Patch Panel: A rack or box where cables are terminated
- usually in 110 punchdowns and interconected with patchcords
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- Horizontal Cabling: The connection from the telecom closet
to the work area outlet (desktop)
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- Backbone Cabling: The cabling that connects all the hubs
in telecom closets or MXCs together
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- Link (Permanent Link): The installed cable plant from work area outlet
jack to the patch panel in the telecom closet
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- Channel: The cable plant including the link plus
patchcords on either end to connect the communications hardware
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- Patchcord: A short length of stranded cable with
a RJ-45 plug on either end, used to connect hardware to the link
or to connect cables in a Patch Panel. Also a short fiber optic cable use for connections.
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- J hook: A hook shaped like the letter J used to suspend
cables
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- Fishtape: Semiflexible rod used to retrieve cables
or pull line
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- Cable
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- The Types Of "Low Voltage"
Copper Cable.
- For information on fiber optic cabling, see the FOA Online Fiber Optic Reference Guide.
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- UTP: Unshielded
twisted pair cable, most commonly comprised of 4 twisted pairs of
copper conductors, graded for bandwidth as "Levels" (from Anixter) or
"Categories" (EIA/TIA 568). Legacy analog phone systems (POTS or plain
old telephone systems) used multipair UTP cables with 25, 50, 100, 200
or more pairs.
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- Category 3,4,5, 5e, 6:
Ratings on the bandwidth performance of UTP cable, derived from
Anixter's Levels program. Category 5e (enhanced) is rated to 100MHz.
Cat 6 standards for UTP are specified at up to 200 MHz. Cat 6A
(augmented) up to 500 MHz has recently been ratified. Cat 7 is also
discussed for the future, but is only standardized as "Class F" in
Europe, not the US. "Categories" called "Classes" in woldwide standards
like ISO and IEC. Cables rated Cat 5 or higher are limited to 4 pairs.
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- A typical Cat 6 cable is shown
below.
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- STP: Shielded twisted pair, specified by IBM for Token
Ring networks and offered by some vendors in higher performance versions than UTP.
ScTP: Screened Twisted Pair, a UTP cable with an overall foil shield to prevent interference.
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- Optical Fiber: Both multimode and singlemode fiber
are included as well. See Fiber Optics, The Basics in the FOA Online Reference Guide or Lennie
Lightwave's Guide to Fiber Optics for more information
on fiber optics.
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- Coax: A type of cable that uses a central conductor,
insulation, outer conductor/shield, and jacket; used for high
frequency communications like CCTV (closed circuit TV)
or CATV (community antenna TV or cable TV). Coax is
not included in TIA-568 but is included in TIA-570 for home use.
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- RG-6/RG-59: 75 ohm coax used for video. RG-6 is
the standard for CATV, RG-59 is used on some short CCTV networks.
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- RG-58: 50 ohm coax used for "Thinnet" Ethernet.
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- HFC: Hybrid fiber-coax CATV network combines coax and
optical fiber
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- Terminations
- The connectors for UTP are also
standard - used on every cable for Cat 3, 5, 5e, 6, but must
be rated for the same performance level, e.g. Cat 6 hardware
on Cat 6 cable.
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- RJ-45:
The popular name of the modular 8 pin connector used with UTP cable in
structured cabling systems. It is used erroneously, as a connector is
only really an RJ-45 if it is terminated with USOC pinout for plain old
telephone service.
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- Jack: The receptacle for a modular plug like the modular 8 pin connector, often used in large quantities in patch panels. (Left in the photo above)
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- Plug: The connector on the end of UTP cable. (Right in the photo above.)
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- Punchdown:
A connecting block that terminates two cables directly, most often used
for connecting incoming multipair cables to 4 pair cables to the
desktop but occasionally for cross connecting 4 pair cables. 110 blocks
are most popular for LANs, 66 blocks for telco, but some installers use
BIX or Krone.
Below - 66 blocks on the left, 110 blocks on the right:
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- Copper Cable Testing
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- After installing the cables,
they must be tested. Every cable, including Cat 3 for telephones,
must be tested for wiremap, but cable certifiers will test for
all the parameters listed below.
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- Wiremap: All eight wires must be connected to
the correct pins, and the test is called a wiremap test.
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- Length: The length must be less than 90 m for
the permanent link and less than 100 m for the channel
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- Attenuation: The reduction in signal strength due
to loss in the cable.
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- NEXT: Near End Cross Talk, or the signal coupled from
one pair to another in UTP cable.
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- ACR: Attenuation to crosstalk ratio, a measure of how
much more signal than noise exists in the link, by comparing
the attenuated signal from one pair at the receiver to the crosstalk
induced in the same pair
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- Return Loss: Reflection from an impedance mismatch
in a copper cable
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- ELFEXT: Equal level far end crosstalk; crosstalk at the
far end with signals of equal level being transmitted.
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- Propagation Delay: The time it takes a signal to go down
the cable.
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- DC Loop Resistance: The DC resistance of the cable in ohms.
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- Delay Skew: The maximum difference of propagation
time in all pairs of a cable.
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- Power Sum Next: Near end crosstalk tested with all pairs
but one energized to find the total amount of crosstalk caused
by simultaneous use of all pairs for communication
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- Power Sum ElFEXT: ELFEXT for the sum of the other 3 pairs
on the 4th pair.
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- PSACR: PowerSum ACR
Alien Crosstalk: Crosstalk from one pair in a cable to the equivalent pair in another cable, a problem with Cat 6A.- Fiber Testing:
Testing optical fiber is much easier. One need only test the loss from
one end to the other, as bandwidth or frequency response is not
generally an issue for premises cabling. More on fiber testing.
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- Then There's The Electronics
That Makes It All Work Over The Cabling As A Network
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- Hub: The electronic box that connects to all the horizontal
cables which are them connected by backbone cabling, enabling
any PC to talk to any other
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- Switch: A device like a hub but connects any two devices
directly, allowing multiple connections simultaneously
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- Bridge: A device that connects two or more sets
of network cables
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- Router: A smart switch that connects to the outside
world
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- Ethernet:: A 10, 100 or 1000 Megabit per second
local area network (LAN) that is by far the most popular LAN
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- 10Base-T: 10 MB/s Base Band Transmission, 100 meters
max, segment length on Cat 3, or better twisted pair cable
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- 100Base-TX: 100 MB/s Base Band Transmission, 100
meters max, segment length on Cat 5, twisted-pair cable, also
referred to as Fast Ethernet
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- 1000Base-T: Gigabit Ethernet on Cat 5e UTP
10GBase-T: 10 Gigabit Ethernet on Cat 6A UTP- All versions of Ethernet
also have fiber optic connection standards. More.
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- Power over Ethernet: The IEEE 802.3 Ethernet committee added
provisions for powering devices off the spare pairs in a 4-pair
UTP cable. Since Ethernet up to 100Base-TX uses only pairs 2
and 3, pairs 1 and 4 are available to provide power. Pair 1 (pins
4/5) is the + conductor, pari 4 (pins 7/8) is the - conductor.
Almost 13 watts of power are available, adequate for powering
local swithches or hubs that can serve several users locally
from one UTP cable, thus saving cabling costs.
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- Wireless Is NOT Wireless
- Most LANs today include wireless
access points. Wireless is by no means wireless, as it requires
wiring to connect it to the network. It merely replaces patchcords
with a wireless link to allow roaming within a limited area.
Wireless requires many access points connected (over wire or
fiber) into the backbone.
- WiFi is the popular name for IEEE 802.11 standard used by most portable computers and many other mobile devices.
- Bluetooth (IEEE 802.15) is
a limited distance network for consumer devices. It has been used to
connect a wireless printer or mouse to a PC, wireless headsets to cell
phones and stereos, cell phones to cars for hands-free operation,
digital cameras to printers, etc.
- WiMAX (IEEE 802.16)
is a further development of wireless network technology that expands
the data capacity of wireless and it’s distance capability.
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- Test Equipment and Tools For Cabling:
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- Digital multimeter: A simple tester that measures if the
cable is shorted and whether or not it is open
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- Wire Mapper: Checks each wire to make sure they are
terminated in the correct order
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- Cable Certification Tester: Tests everything, wiremap, length, attenuation
and crosstalk in one connection, gives you a pass/fail result
- Cable Verification Tester: A device that runs network signals over installed cabling to see if the cabling can transmit network data without error.
- TDR: Time domain reflectometer, a testing device used
for copper cable that operates like radar to find length, shorts
or opens, and impedance mismatches
Fiber optics: Testing is done with visual tracers/fault locators, optical loss test sets and OTDRs. Here is more information on fiber testers.
Test your comprehension with the section quiz
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