FOA Guide


Premises 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.
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.

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.
Structured Cabling is the standardized architecture and components for communications cabling specified by the EIA/TIA TR42 committee and used as a voluntary standard by manufacturers to insure interoperability.

Cabling is designed to provide connections for networks, primarily LANs- local area networks - used for connecting Ethernet and WiFi Devices.

Ethernet is standardized by IEEE 802.3 with versions for many speed levels and cabling types

WiFi is a standard (IEEE 802.11) used for wireless communications that has access points (antennas) connected on Ethernet networks for wireless devices.

Network Architectures:
Most networks today use a "star" network, but prior networks used busses or rings.

star   ethernet bus  ring architecture 
Star (L), bus (center) and ring (R) network architectures. Networks today use the star network. Ethernet started as a bus network on coax cable. IBM used the ring architecture on Token Ring networks and it was later used for FDDI (fiber distributed data interface.)

HFC: Hybrid fiber-coax CATV network combines a fiber optic backbone and coax drops to the subscribers.

Read more: Networks

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.

Standards are voluntary, written to ensure interoperability of products from different sources, They are not legal requirements like building or fire codes which are required by local laws. 

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.
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 which came later than TIA, 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)
EIA/TIA 570: For residential cabling.
EIA/TIA 606: cabling system administration (documentation) (ISO/IEC 14763-1)
EIA/TIA 607: Grounding and bonding
Standards are not code! They are voluntary interoperability specifications. However every installation must be compliant to local building codes for safety!
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.

Read More: Standards

Structured Cabling Architecture (TIA-568)
cabling architecture

Traditional structured cabling (above) defined in TIA 568 and adopted by ISO/IEC 11801 includes UTP copper cabling and fiber optics, including centralized fiber optics. The standards are based on a maximum length of UTP cabling of 100 meters, 90 meters installed in the building (the "permanent link") and 10 meters of patchcords.

The standards have been updated to recognize passive optical LANs (POLs) based on fiber to the home (FTTH) technology (below) using fiber optic passive splitters instead of electronic network switches.

Passive OLAN (optical LAN) using PON (passive optical network) from FTTH (fiber to the home)


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. See below or the link.
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!
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
Intermediate Cross-Connect (IXC) : A room in between the TC and MXC where cables are terminated
(TIA has changed these terms to the ones in the diagram below but the former terms are still widely used because they are well understood and descriptive. Here are the new terms.)

T568C terms

wall outlet wall outlet
Work Area Outlet: The jack on the wall which is connected to the desktop computer by a patchcord. Often integrated into modular furniture.
patch panel
Patch Panel: A rack or box where cables are terminated - usually in 110 punchdowns and interconected with patchcords
Patchcord: A short length of UTP 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 with connectors uses for connecting cables or equipment.
Horizontal Cabling: The connection from the telecom closet to the work area outlet (desktop)
Backbone Cabling: The cabling that connects all the hubs in telecom closets or MXCs together
Link (Permanent Link): The installed cable plant from work area outlet jack to the patch panel in the telecom closet (definition used for testing the permanently installed cable plant.)
Channel: The cable plant including the link plus patchcords on either end to connect the communications hardware (a definition used for testing the installed cable plus patchcords connecting equipment.)

J hook: A hook shaped like the letter J used to suspend cables
Fishtape: Semiflexible rod used to retrieve cables or pull line
The Types Of "Low Voltage" Copper Cable. Cabling standards cover UTP (unshielded twisted pair), ScTP (screened twisted pair), STP (shielded twisted pair) and fiber optics. Coax cable is used in premises cabling for video, especially residential TV or security.

For more  information on fiber optic cabling, see the FOA Online Fiber Optic Reference Guide.
UTP: Unshielded twisted pair cable, is 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.

A typical Cat 6 UTP cable is shown below. Notice the difference in the twist rates of the pairs - that difference helps reduce crosstalk between the pairs at higher frequencies.
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.

Category-Rated Cables: Category 3,4,5, 5e, 6, 6A, 8: Ratings on the bandwidth performance level of UTP cable, originally derived from Anixter's Levels program. Cat 8 is a new short length cable for data center connections of servers and switches. "Categories" are called "Classes" in worldwide standards like ISO and IEC.  Cables rated Cat 5 or higher are limited to 4 pairs.



 Cat 5
 Cat 5e
(Class D)
 Cat 6 (6A)
(Class E)
(Class F)
Cat 8
(Class I, II)
 Supports networks  100Base-T  1000Base-T
None currently considered
10-40 Gb/s
 Test Frequency  100 MHz  100MHz  250 MHz
(500 MHz)
 600 MHz  Terahertz
 Length  100 meters  100 meters  100 meters  100 meters
30 meters
 RJ-45 Compatible  yes  yes
 No Some
 Field Tester Requirement:  Level 2  Level 2e  Level 3 (3e)  Level 4
Level 2G
Ethernet at 10Mb/s and 100 Mb/s used only 2 pairs of the 4 pairs in a UTP cable, but gigabit Ethernet required transmission on all four pairs, as do all faster versions of Ethernet.

Single Pair Ethernet: IEEE has created a standard primarily for industrial Ethernet that uses a single pair cable for 10, 100 or 1000Mb/s networks. It uses a different style of cable and connector for rugged environments. A special power-over-Etherent standard called PDL - power over data line - has been developed for it also.

Read More: UTP Cables

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).

While early LANs used coax cable for its additional bandwidth, it is not included in TIA-568, but is included in TIA-570 for home use.
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.
RG-58: 50 ohm coax used for "Thinnet" Ethernet.

Read More: Coax Cable

Fiber Optics: Optical fiber carries signals as pulses of light over thin strands of glass or plastic instead of copper wire.

fiber optic cable

Optical fiber is characterized by the size of the light-carrying core and the cladding.
all fibers

Multimode optical fiber: larger core fiber used for short, relatively low speed links (~<10G)

Singlemode optical fiber: small core fiber used for longer distance linkes with almost unlimited bandwidth.

HCS/PCS - Hard-clad or plastic-clad silica fiber has a glass core and plastic cladding. It is used for short, slow links.

Plastic optical fiber (POF) large core plastic fiber used for short, relatively slow links.

Fiber Type
Original LAN fiber, now mostly obsolete
OM2/3/4/5 (G.651.1)
Most widely used multimode fiber, laser optimized
Singlemode (G.652)
Used for all OSP links and high speed LANs, Passive OLANs and data center connections
Read more: Fiber Optics in Premises Cabling


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.

UTP plug and jack  UTP termination
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 (POTS). Category rated terminations use the modular 8-pin connector with the T568A or T568B pin configuration shown above for better performance.
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)
Plug: The connector on the end of UTP cable. (Right in the photo above.)
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.

66 blocks on the left, 110 blocks on the right:

66 block  110 block
Using punchdown tools to terminate a 66 block (left) and a 110 block (right)

To reduce crosstalk and signal loss, twists must be maintained as close as possible to the terminations, with no more than 1/2 inch (13mm) of the pair untwisted.

Read more: UTP Terminations

Optical Fiber Terminations

Fiber Optic Terminations are generally (from left) SC, ST or LC connectors. Multifiber links use MPO Connectors

Power Over Ethernet

The IEEE 802.3 Ethernet committee created a standard for powering network devices such as wireless access points, VoIP phones and surveillance cameras off the copper pairs in a 4-pair UTP cable. PoE uses a 48 volt power supply and requires cable of Cat 5 rating or higher. Power may be delivered using what are called midspan devices, dedicated PoE power supplies that can be plugged into links or even patch panels, as well or endspan devices, typically switches designed to provide power as well as function as anEthernet switch.

Power over Ethernet Standards

IEEE Standard

Max Current Per Pair

Number of Pairs Used

Power At Source

Power At Device



802.3at Type 1

350 mA


15.4 W

13 W


802.3at Type 2

600 mA


30 W

25.5 W

PoE++ or 4PPoE

802.3bt Type 3*

600 mA


60 W

51 W

PoE++ or 4PPoE

802.3bt Type 4*

960 mA


99 W

71.3 W

Copper Cable Testing
After installing the cables, they must be tested. Every UTP, ScTP or STP cable, including Cat 3 for telephones, must be tested for wiremap, but cable "certifiers" will test for all the parameters specified in the standards (listed below.) A third type of tester, called a verifier, tests the cabling to see if it will transmit date for specific networks like Gigabit Ethernet.

Testing for TIA568 cabling standards requires the use of a cable certifier to confirm all the performance parameters of the cabling.

Permanent Link

Most testing tests only the "permanent link," the cabling installed in the building. Sometimes testing also requires testing the "Channel" which includes the patchcords at either end.

  wiremap     UTP termination

Wiremap: All eight wires must be connected to the correct pins, and the test is called a wiremap test.
Length: The length must be less than 90 m for the permanent link and less than 100 m for the channel
Attenuation: The reduction in signal strength due to loss in the cable.
NEXT: Near End Cross Talk, or the signal coupled from one pair to another in UTP cable.
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
Return Loss: Reflection from an impedance mismatch in a copper cable
ELFEXT: Equal level far end crosstalk; crosstalk at the far end with signals of equal level being transmitted.
Propagation Delay: The time it takes a signal to go down the cable.
DC Loop Resistance: The DC resistance of the cable in ohms.
Delay Skew: The maximum difference of propagation time in all pairs of a cable.
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
Power Sum ElFEXT: ELFEXT for the sum of the other 3 pairs on the 4th pair.
Alien Crosstalk: Crosstalk from one pair in a cable to the equivalent pair in another cable, a problem with Cat 6A.

Test Equipment For Copper Cabling:
Digital multimeter: A simple tester that measures voltage, current and resistance. It can be used to test if the cable is shorted or open, often the only test used on coax cable.
Wire Mapper: Checks each wire to make sure they are terminated in the correct order
Cable Certification Tester: Tests all specifications in the standards: 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. Does not test specifications for standards.

TDR: Time domain reflectometer, a testing device used for copper cable that operates like radar to find length, shorts or opens, and impedance mismatches

Read More: UTP Testing

Fiber Optic Cable Testing

Testing optical fiber is much easier. One need only tests polarity/continuity and the loss from one end to the other, as bandwidth or frequency response is not generally an issue for premises cabling.
Fiber optic testing is done with visual inspection microscopes to inspect connector cleanliness and condition, visual fault locators for tracing fibers and finding breaks,  optical loss test sets (OLTS) to measure insertion loss and OTDRs for troubleshooting.

fiber optic los testing 
Light source and power meter (OLTS) testing the loss of a cable

Here is more information on fiber testing.


The LAN Electronics That Makes It All Work Over The Cabling As A Network
Hub:  electronic box that connects to all the horizontal cables which are them connected by backbone cabling, enabling any PC to talk to any other, mostly replaced by switch.
Switch: A device like a hub but connects any two devices directly, allowing multiple connections simultaneously
Bridge: A device that connects two or more sets of network cables
Router: A smart switch that connects to the outside world
Ethernet:: A 10, 100 or 1000 Megabit per second local area network (LAN) that is by far the most popular LAN.  Ethernet:: A local area network (LAN) that is by far the most popular LAN. Versions exist for transmission from 10Mb/s to 100Gb/s. All versions of Ethernet also have fiber optic connection standards.

Wireless Is NOT Wireless

All 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 UTP cabling or fiber) into the LAN Ethernet backbone. (See structured cabling diagram above.)
WiFI access points indoors in a convention center and outdoors in a city park
WiFi is the popular name for IEEE 802.11 standard used by most portable computers and other mobile devices.

WiFi access points in a LAN can usually be powered by PoE (power over Ethernet, see above)

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.
Dstributed Antenna Systems (DAS): Indoor antennas for cell phones which may use structured cabling. 4G, 5G and other cellular standards can be brought indoors where 80% of all cell phone calls originate using DAS. DAS can usually share cabling
Read More: Wireless

Test your comprehension with this quiz   

Premises Cabling Website Contents

Each page will open in a new window

Overview of Premises Cabling and Standards  
UTP Cables   Power Over Ethernet.
UTP Terminations,  (Tutorial). UTP Termination 
UTP Installation VHO  66 Block, 110 Block, Jacks, Plugs  
UTP Testing,  UTP Wiremapping  
Coax Cable  VHO Coax Termination  
Fiber Optics in Premises Cabling
Design, New T-568-C Nomenclature
Premises Cabling Installation
Table of Contents: The FOA Guide


(C)2021, The Fiber Optic Association, Inc.