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Cable Colors

The cabling administration standard (EIA-606) lists the colors and functions of data cabling as:

Horizontal voice cables	Blue
Inter-building backbone	Brown
Second-level backbone	Gray
Network connections and auxiliary circuits	Green
Demarcation point, telephone cable from Central Office	Orange
First-level backbone	Purple
Key-type telephone systems	Red
Horizontal data cables, computer & PBX equipment	Silver or White
Auxiliary, maintenance & security alarms	Yellow

Category Cables

The Category Rating System was developed by TIA as a response to the industry's request for higher data rate specifications on applications over unshielded (UTP) and shielded (STP) twisted pair.
This rating systems has been integrated into the body of the EIA/TIA-568A standard document. The category rating system only applies to 100 ohm UTP and STP wiring systems. EIA/TIA-568A also allows 150 ohm STP (also called type I) and 62.5/125 um multi-mode optical fiber.

Category 3 Cable

Category 3 is characterized to 16 MHz and supports applications up to 10 Mbps. Applications may range from voice to 10BaseT.

Category 5 Cable

Category 5 is characterized to 100 Mhz and supports applications up to 100 Mbps. Applications may range from voice to TP-PMD.

Enhanced Category 5

Enhanced Category 5 is still characterized to 100 Mhz and supports applications up to 100 Mbps. However, Enhanced Category 5 provides additional NEXT margin (sometimes referred to as headroom) over the specified frequency band from 1 MHz to 100 MHz. The total noise power with all pairs energized (usually specified as Power Sum NEXT) meets or exceeds the Category 5 specification for worst pair-to-pair NEXT. It also provides improved ELFEXT (Equal Level Far-End Crosstalk) and Return Loss Performance.

Category Safety Requirements
These Safety Requirements are valid for both Category 3 and 5 applications:

Safety Requirements:
A. UL 1459 (Telephone)
B. UL 1863 (Wire and Jacks)
C. NEC 1996, Article 800-4
Availability:
A. 22 AWG and 24 AWG
B. Type: CMR/MPR or CMP/MPP
C. Available in solid conductors

BASIC / CHANNEL LINK ATTENUATION
Frequency (MHz)	Category 3 (dB)	Category 4 (dB)	Category 5 (dB)
1	3.2/4.2	2.2/2.6	2.1/2.5
4	6.1/7.3	4.3/4.8	4/4.5
8	8.8/10.2	6/6.7	5.7/6.3
10	10/11.5	6.8/7.5	6.3/7
16	13.2/14.9	8.8/9.9	8.2/9.2
20	---/---	9.9/11	9.2/10.3
25	---/---	---/---	10.3/11.4
31.25	---/---	---/---	11.5/12.8
62.5	---/---	---/---	16.7/18.5
100	---/---	---/---	21.6/24

BASIC / CHANNEL LINK NEXT LOSS (Pair - To - Pair)
Frequency (MHz)	Category 3 (dB)	Category 4 (dB)	Category 5 (dB)
1	40.1/39.1	54.7/53.3	60/60
4	30.7/29.3	45.1/43.3	51.8/50.6
8	25.9/24.3	40.2/38.2	47.1/45.6
10	24.3/22.7	38.6/36.6	4.5/44
16	21/19.3	35.3/33.1	42.3/40.6
20	---/---	33.7/31.4	40.7/39
25	---/---	---/---	39.1/37.4
31.25	---/---	---/---	37.6/35.7
62.5	---/---	---/---	32.7/30.6
100	---/---	---/---	29.3/27.1

Circuit Protection

· Protectors are surge arresters designed for the specific requirements of communications circuits. They are required for all aerial circuits not confined with a block. (Block here means city block.) They must be installed on all circuits with a block that could accidentally contact power circuits over 300 volts to ground. They must also be listed for the type of installation. Other requirements are the following:

· Metal Sheaths of any communications cables must be grounded or interrupted with an insulating joint as close as practicable to the point where they enter any building (such point of entrance being the place where the communications cable emerges through an exterior wall or concrete floor slab, or from a grounded rigid or intermediate metal conduit).

· Grounding conductors for communications circuits must be copper or some other corrosion-resistant material, and have insulation suitable for the area in which it is installed.

· Communications grounding conductors may be no smaller than No. 14.

· The grounding conductor must be run as directly as possible to the grounding electrode, and be protected if necessary.

· If the grounding conductor is protected by metal raceway, it must be bonded to the grounding conductor on both ends.

Grounding electrodes for communications ground may be any of the following:

1. The grounding electrode of an electrical power system.

2. A grounded interior metal piping system. (Avoid gas piping systems for obvious reasons.)

3. Metal power service raceway.

4. Power service equipment enclosures.

5. A separate grounding electrode.

If the building being served has no grounding electrode system, the following can be used as a grounding electrode:

1. Any acceptable power system grounding electrode.

2. A grounded metal structure.

3. A ground rod or pipe at least 5 feet long and 1/2 inch in diameter. This rod should be driven into damp (if possible) earth, and kept separate from any lightning protection system grounds or conductors.

Connections to grounding electrodes must be made with approved means. If the power and communications systems use separate grounding electrodes, they must be bonded together with a No. 6 copper conductor. Other electrodes may be bonded also. This is not required for mobile homes.

For mobile homes, if there is no service equipment or disconnect within 30 feet of the mobile home wall, the communications circuit must have its own grounding electrode. In this case, or if the mobile home is connected with cord and plug, the communications circuit protector must be bonded to the mobile home frame or grounding terminal with a copper conductor no smaller than No. 12.

Common Ethernet Systems

10BASE-5 or Thick Ethernet

· 10BASE-5 is the original Ethernet system. It employs a quarter of an inch diameter, 50 ohm coax cable ( with minimum bend radius of 10 inches). 10BASE-5 segments can run in length up to 500 meters with as many as 100 transceiver connections spaced at lease 2.75 yards apart.

· 10BASE-5 transceivers access the media by piercing the thick coaxial cable. These transceiver taps are known as vampire taps. Since they don't actually require breaking the physical cable, the electrical signals over the cable are typically fairly clean.

· 10BASE-5 systems were originally envisioned to be cheap and fairly easey to build. The large cable needed simply to be run by rooms where computing equipment would be located. Taps would be made into the cable by using external transceivers. As it turned out, the requirement of an external transceiver and the thick cable, which was expensive and difficult to work with, limited the use of 10BASE-5.

10BASE-2 (Thin Ethernet and Cheapernet)

· Thin Ethernet was a fairly popular specification and is still used in many environments today. With a maximum segment length of 203.5 yards, it requires that the 50 ohm cable be only .2 inches thick ( a bend radius of two inches). It also uses standard BNC connectors and "T's" to provide access to the media. Typically, T's are connected directly to the back of network interface cards, thus eliminating the need for an external transceiver.

· A maximum of 30 transceivers may be inserted onto a Thin Ethernet segment and must be spaced at least 20 inches apart. 3Com hardware is able to handle slightly longer segments, up to 220 yards in length. Unfortunately, mixing other vedor's equipment into an environment where cable runs exceed 203.5 yards can cause problems. For this reason, keeping total lengths to 203.5 yards is recommended

Data Communications Definitions

Attenuation

A reduction is strength or deterioration of an electrical signal as it passes through a transmission medium. Attenuation generally increases with frequency, cable length and the number of connections in a circuit. Attenuation is measured in decibels (dB). In optical fiber, a diminution of the signal is only a function of length traveled.

Backbone

Generally, the more permanent part of a communications network which carries the heaviest traffic. Usually a vertical arrangement that connects floors in a multi-story building. however, the same function may be served by a lateral backbone for horizontal distribution in a low, wide building.

Bend Radius

The radius a cable can bend before the risk of breakage or increase in attenuation occurs.

Bus

1)A data path shared by many devices. 2)A linear network topology in which all workstations are connected to a single cable. On a bus network, such as Ethernet, all workstations receive all transmissions; only the workstation that the information is addressed to will use the information. Contrast with ring and star.

Crossover

A conductor which connects to a different pin number at each end.

Crosstalk

The phenomenon in which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel, generally related to wire placement, shielding, and transmission techniques.

Ethernet

A baseband LAN used for connecting computers and terminals within the same building.

Home Runs

A pathway or cable between two locations without a point of access in between.

Impedance

A unit of measure, expressed in Ohms, of the total opposition (resistance, capacitance and inductance) offered to the flow of an alternating current.

Jumper

An assembly of twisted pairs without connectors, used to join telecommunications circuits/links at the cross-connect.

Local Area Network (LAN)

A non-public data communications network confined to a limited geographic area (usually within a few miles), used to provide communication between computers and peripherals. The area served may consist of a single building, a cluster of buildings, or a campus-type arrangement. It is owned by its user, includes some type of switching technology and does not use common carrier circuits - although it may have gateways or bridges to other public or private networks.

Patch Panel

A cross-connect system of matable connectors that facilitates administration.

Token

A unique combination of bits used in LANs to grant permission to a station to transmit. In a ring network, the token circulates continuously; in a bus it must be addressed.

Twisted Pair Cable

A type of communications transmission cable in which two individually insulated wires are twisted around each other to reduce induction (thus interference) from one wire to the other. The pair may be surrounded by a shield, insulating jacket or additional pairs of wires.