Common Terms
Category:
The EIA/TIA 568 standard specifies certain
performance and speed characteristics for structured cabling systems. These
specifications follow a "Category" system, where each Category specifies a
certain level of performance.
The EIA/TIA 568 standard starts with
Category 3, and goes to Category 5. Categories 1 and 2 are not officially
recognized, but are generally used in the cabling industry as being useful at
frequencies of 1 MHz and 4 MHz, respectively. Category 3 specifies a cable rated
for frequencies up to 10 MHz, Category 4 cables are rated at up to 20 MHz, and
Category 5 is rated up to 100 MHz.
Nowadays, Category 3 cable is widely
regarded as being a "voice grade" cable, and most new data installations use
Category 5.
Horizontal Cabling:
This is the
wiring that runs from the telecommunications wiring closet to the workstation
outlet. For each workstation outlet, there will be one or more cable runs back
to the wiring closet, depending on how many jacks are needed at the workstation
outlet.
Backbone Cabling:
This is the cabling
that provides the interconnection between wiring closets and equipment rooms,
whether in the same or different buildings. It includes the backbone cabling
itself, as well as cross-connects, mechanical terminations, and patch cables
used to provide backbone-to-backbone cross-connection.
Connecting Hardware:
Connecting hardware is
used to terminate the horizontal wiring in the wiring closet or at the
workstation outlet. Patch panels, used in the wiring closet, and wall plates,
used at the desktop, fall into this category. The EIA/TIA 568 standard specifies
RJ-45 jacks to be used in these types of products. Patch panels provide multiple
RJ-45 jacks, often in multiples of twelve, and are designed to fit into standard
racks or cabinets with 19" mounting rails. Wall plates come in a variety of
types ranging from single outlet, flush mount styles to multi-outlet,
multi-media surface mount versions. Most connecting hardware will also
accommodate other types of connectors, such as RJ-11, BNC, and fiber optic, for
use in telephone or non-EIA/TIA applications.
Category 5 (or 100 MHz
capable) connecting hardware is routinely constructed using a circuit board
design with RJ-45 jacks mounted on the front and AT&T 110 type contacts
mounted on the rear. The 110 contact uses insulation displacement technology to
terminate the horizontal wiring to the RJ-45 jack. Although the AT&T 110
contact is the most popular method of terminating the horizontal wiring to the
jack, other types, such as the Krone and 66 contact, are also used by some
manufacturers.
Patch Cables:
Patch cables are used to make the
physical connection between the connecting hardware and the network or
telecommunications equipment. At the wiring closet, patch cables are used to
facilitate fast and easy moves, changes or additions to the network. At the
desktop, they make connection to user equipment like network interface
cards.
It is debatable as to whether patch cables can be considered a
part of the structured wiring system. By definition, they are not because their
use changes as the needs of the network users change, but they are so well
defined by the ANSI/TIA/EIA-568-A standard that it is an easy intellectual jump
to include them in any discussion of structured wiring.
| Definitions + Information | |
| Category 5 Cable (UTP) (Unshielded Twisted Pair) | A multipair (usually 4 pair) high performance cable that consists of twisted pair conductors, used mainly for data transmission. Note: The twisting of the pairs gives the cable a certain amount of immunity from the infiltration of unwanted interference. category-5 UTP cabling systems are by far, the most common (compared to SCTP) in the United States. Basic cat 5 cable was designed for characteristics of up to 100 MHz. Category 5 cable is typically used for Ethernet networks running at 10 or 100 Mbps. |
| Category 5 E Cable (enhanced) | Same as Category 5, except that it is made to somewhat more stringent standards (see comparison chart below). The Category 5 E standard is now officially part of the 568A standard. Category 5 E is recommended for all new installations, and was designed for transmission speeds of up to 1 gigabit per second (Gigabit Ethernet). |
| Category 6 | Same as Category 5 E, except that it is made to a higher standard (see comparison chart below). The Category 6 standard is still in the works (as of this writing) and is not yet part of the 568A standard. |
| Category 7 | Same as Category 6, except that it is made to a higher standard (see comparison chart below). The Category 6 standard is still in the works (as of this writing) and is not yet part of the 568A standard. One major difference with category 7's construction (as compared with category 5, 5 E, and 6) is that all 4 pairs are individually shielded, and an overall shield enwraps all four pairs. Category 7 will use an entirely new connector (other than the familiar RJ-45). |
| Category 5 Cable (SCTP) (Screened Twisted Pair) | Same as above, except that the twisted pairs are given additional protection from unwanted interference by an overall shield. There is some controversy concerning which is the better system (UTP or SCTP). Category 5 SCTP cabling systems require all components to maintain the shield, and are used almost exclusively in European countries. |
| Category 5, RJ45 jack (Work Area Outlet) |
An 8 conductor, compact, modular, female jack that is used to terminate category-5 cable at the user (or other) location. The jack is specifically engineered to maintain the performance of cat 5 cabling. |
| Category 5 Patch Panel | A Category 5 Patch Panel is basically just a series of many category-5 jacks, condensed onto a single panel. Common panel configurations are 12, 24, 48, and 96 ports. Patch panels are typically used where all of the horizontal cable sections meet, and are used to connect the segments to the Network Hub. |
| Category 5 Patch Cable | A Category 5 Patch Cable consists a length of cat 5 cable with an RJ-45 male connector, crimped onto each end. The cable assembly is used to provide connectivity between any two category-5 female outlets (jacks). The two most common are from hub to patch panel, and work area outlet (jack) to the computer. |
| EIA/TIA 568A Standard | This standard was published in July of 1991. The purpose of EIA/TIA 568A, was to create a multiproduct, multivendor, standard for connectivity. Prior to the adoption of this standard, many "proprietary" cabling systems existed. This was very bad for the consumer. Among other things, the standard set the minimum requirements for category 5 cable and hardware. The 568 "standard" is not to be confused with 568A or 568B wiring schemes, which are themselves, part of the "568A standard". |
| 568A and 568B Wiring Schemes | When we refer to a jack or a patch panel's wiring connection, we refer to either the 568A, or 568B wiring scheme, which dictates the pin assignments to the pairs of cat 5 cable. It is very important to note that there is no difference, whatsoever, between the two wiring schemes, in connectivity or performance when connected form one modular devise to another (jack to Patch panel, RJ-45 to RJ-45, etc.), so long as they (the two devises) are wired for the same scheme (A or B). The only time when one scheme has an advantage over the other, is when one end of a segment is connected to a modular devise, and the other end to a punch block. In which case, the 568A has the advantage of having a more natural progression of pairs at the punch block side. More on 568 A&B later on. |
| Four Pairs |
|
| Wiremap | This is the most basic test that can be performed on a category-5 segment. Wiremap tests for the basic continuity between the two devices. In 568A or B, all eight pins of each devise should be wired straight through (1 to 1, 2 to 2, 3 to 3, etc.). A wiremap (continuity) test, should also test for absence of shorts, grounding, and external voltage. |
| Crosstalk | Crosstalk is the "bleeding" of signals carried by one pair, onto another pair through the electrical process of induction (wires need not make contact, signals transferred magnetically). This is an unwanted effect, that can cause slow transfer, or completely inhibit the transfer of data signals over the cable segment. The purpose of the wire twists, in category 5 cable is to significantly reduce the crosstalk, and it's effects. Two types are: NEXT (Near End Crosstalk), and FEXT (Far End Crosstalk). Fiber Optic cable is the only medium that is 100% immune to the effects of crosstalk. |
| Ambient Noise or Electromagnetic Interference (EMI) | Similar to crosstalk, in that it is an unwanted signal that is induced into the cable. The difference is that ambient noise (or EMI) is typically induced from a source that is external to the cable. This could be an electrical cable or devise, or even an adjacent category 5 cable. |
| Attenuation | Attenuation is the loss of signal in a cable segment due to the resistance of the wire plus other electrical factors that cause additional resistance (Impedance and Capacitance for example). A longer cable length, poor connections, bad insulation, a high level of crosstalk, or ambient noise, will all increase the total level of attenuation. The 568A standard, specifies the maximum amount of attenuation that is acceptable in a category-5 cable segment. |
