TIA / EIA-568

trgtfgfg History[edit]

TIA/EIA-568 was developed through the efforts of more than 60 contributing organizations including manufacturers, end-users, and consultants. Work on the standard began with the EIA, to define standards for telecommunications cabling systems. EIA agreed to develop a set of standards, and formed the TR-42 committee,[3] with nine subcommittees to perform the work. The work continues to be maintained by TR-42 within the TIA.

The first revision of the standard, TIA/EIA-568-A.1-1991 was released in 1991. The standard was updated to revision B in 1995. The demands placed upon commercial wiring systems increased dramatically over this period due to the adoption of personal computers and data communication networks and advances in those technologies. The development of high-performance twisted pair cabling and the popularization of fiber optic cables also drove significant change in the standards. These changes were first released in a revision C in 2009 which has subsequently received minor maintenance updates.[4]

Goals[edit]

TIA/EIA-568 defines structured cabling system standards for commercial buildings, and between buildings in campus environments. The bulk of the standards define cabling types, distances, connectors, cable system architectures, cable termination standards and performance characteristics, cable installation requirements and methods of testing installed cable. The main standard, TIA/EIA-568-C.1 defines general requirements, while -568-C.2 focuses on components of balanced twisted-pair cable systems . TIA-568-C.3 addresses components of fiber optic cable systems, and -568-C.4, addressed coaxial cabling components.[5]

The intent of these standards is to provide recommended practices for the design and installation of cabling systems that will support a wide variety of existing and future services. Developers hope the standards will provide a lifespan for commercial cabling systems in excess of ten years. This effort has been largely successful, as evidenced by the definition of category 5 cabling in 1991, a cabling standard that (mostly) satisfied cabling requirements for 1000BASE-T, released in 1999. Thus, the standardization process can reasonably be said to have provided at least a nine-year lifespan for premises cabling, and arguably a longer one.

All these documents accompany related standards that define commercial pathways and spaces (TIA-569-C-1, February 2013), residential cabling (ANSI/TIA-570-C, August 2012), administration standards (ANSI/TIA-606-B, June 2012), grounding and bonding (TIA-607-B-2, August 2013), and outside plant cabling (TIA-758-B, April 2012).

Cable categories[edit]

The standard defines categories of unshielded twisted pair cable systems, with different levels of performance in signal bandwidth, attenuation, and cross-talk. Generally increasing category numbers correspond with a cable system suitable for higher rates of data transmission. Category 3 cable was suitable for telephone circuits and data rates up to 16 million bits per second. Category 5 cable, with more restrictions on attenuation and cross talk, has a bandwidth of 100 MHz.[6] The 1995 edition of the standard defined categories 3, 4, and 5. Categories 1 and 2 were excluded from the standard since these categories were only used for voice circuits, not for data.[7]

Structured cable system topologies[edit]

TIA/EIA-568-C defines a hierarchical cable system architecture, in which a main cross-connect (MCC) is connected via a star topology across backbone cabling to intermediate cross-connects (ICC) and horizontal cross-connects (HCC). Telecommunications design traditions utilized a similar topology, and many people refer to cross-connects by their older, nonstandard names: "distribution frames" (with the various hierarchies called MDFs, IDFs and wiring closets). Backbone cabling is also used to interconnect entrance facilities (such as telco demarcation points) to the main cross-connect. Maximum allowable backbone fibre distances vary between 300m and 3000m, depending upon the cable type and use.

Horizontal cross-connects provide a point for the consolidation of all horizontal cabling, which extends in a star topology to individual work areas such as cubicles and offices. Under TIA/EIA-568-B, maximum allowable horizontal cable distance is 90m of installed cabling, whether fibre or twisted-pair, with 100m of maximum total length including patch cords. No patch cord should be longer than 5m. Optional consolidation points are allowable in horizontal cables, often appropriate for open-plan office layouts where consolidation points or media converters may connect cables to several desks or via partitions.

At the work area, equipment is connected by patch cords to horizontal cabling terminated at jackpoints.

TIA/EIA-568 also defines characteristics and cabling requirements for entrance facilities, equipment rooms and telecommunications room.

T568A and T568B termination[edit]

Perhaps the widest known and most discussed feature of TIA/EIA-568 is the definition of pin/pair assignments for eight-conductor 100-ohm balanced twisted-pair cabling, such as Category 3, Category 5 and Category 6 unshielded twisted-pair (UTP) cables. These assignments are named T568A and T568B and they define the pinout, or order of connections, for wires in 8P8C (often incorrectly referred to as RJ45) eight-pin modular connector plugs and sockets. Although these definitions consume only one of the 468 pages in the standards documents, a disproportionate amount of attention is paid to them. This is because cables that are terminated with differing standards on each