What Is UTP Cable - Unshielded Twisted Pair

 

UTP is defined as Unshielded Twisted Pair cable. UTP cable is characterized as a 100 ohm copper cable that is constructed with 2 to 1800 unshielded twisted pairs, all of which are surrounded by an outer jacket. No metallic shield is employed in these cables. As a result, the cable is made small in diameter, but it is left unprotected against electrical interference. The twisting of the pairs is utilized to improve immunity to electrical noise and EMI.
(Cat 5e and Cat 6 UTP Patch Cables can be obtained from us)

 

 

For horizontal cabling, four-pair construction is typically used, as is illustrated below.

 

Backbone cables are generally constructed with pair counts that are incremented in multiples of 25, since multi-pair UTP cables are built around 25-pair binder groups. A backbone UTP cable is demonstrated in the following illustration.

 

The copper conductor used in both horizontal and backbone UTP cables is sized as either 22 AWG or 24 AWG. The 24 AWG size is most commonly encountered; however, for higher-performance requirements, such as those met by Category 6 UTP, the larger 23 AWG copper wire is often employed to ensure enhanced signal integrity and performance.

 

 

As indicated by its name, the solid conductor UTP cable is constructed with a single, solid copper wire for each conductor. This design is valued not only for the physical strength and ease of handling it provides but also for its superior electrical characteristics, which are maintained stably across a wider range of frequencies. Solid conductors are characterized by lower DC resistance and reduced susceptibility to high-frequency effects, attributes that are afforded by their larger diameters. Consequently, solid conductor cables are enabled to support longer transmission distances and higher data rates when compared to their stranded counterparts. It is for these reasons that solid conductor cables are specified for permanent installations in both horizontal and backbone cabling subsystems.

In contrast, stranded-conductor UTP cables are predominantly utilized as patch cables within work areas or telecommunication rooms. These are the cables that are most frequently handled directly by personnel. In a stranded cable, each conductor is composed not of a single wire, but of a bundle of smaller-gauge wire strands. These strands are arranged helically around a central wire through a manufacturing process known as stranding. The resulting conductor possesses an overall diameter comparable to that of a solid conductor but with a smaller total conducting area, a consequence of the gaps between the strands. The primary advantage conferred by this stranding process is exceptional flexibility, making these cables ideal for applications requiring frequent movement and bending; however, this flexibility is accompanied by a trade-off of marginally higher signal attenuation over extended lengths.

 

UTP cables are extensively deployed in LAN networks. They are commonly used for a diverse array of systems, including voice communications, low-speed and high-speed data transmission, audio and paging systems, as well as building automation and control systems. UTP cable can be effectively implemented in both the horizontal and backbone cabling subsystems, providing a versatile and cost-effective connectivity solution.

 

UTP cables were originally developed for analog voice applications, which are inherently robust and less susceptible to corruption by electrical noise. However, as the demand for digital data transmission grew, UTP cables were required to be engineered to higher performance standards. This evolution led to the creation of distinct categories, or grades, of UTP cables over the years. Lower categories are referred to as voice grade, while higher categories are designated as data grade. The progression of these standards is detailed in the following table, which outlines the various UTP categories, their associated business applications, and corresponding performance specifications.

 

Note:
It should be noted that the TIA/EIA-568 standard officially recognized only cables of Category 3 ratings and above. The terms Category 1 and Category 2 are considered misnomers, likely adopted from the "Levels" grading system originally defined by the distributor Anixter International. Category 1 cable was used exclusively for basic voice-grade telephone networks. Anixter Level 2 (often called Cat 2) was an early UTP grade capable of transmitting data at up to 4 Mbit/s, and it was used in networks like ARCnet and 4 Mbit/s token ring, though it is now considered obsolete.

 

Category	Grade	Business Application	Frequency Range
Category 1	voice grade	Used exclusively for voice-grade telephone networks; not suited for data transmissions.	750 kHz
Category 2	voice grade	Utilized for telephone networks and early IBM dumb-terminal connections to mainframe computers.	1 MHz
Category 3	data grade	Deployed for 10Mbps Ethernet, 4Mbps Token Ring, 100BaseT4 Fast Ethernet, and 100VG Any LAN networks.	16 MHz
Category 4	data grade	Employed in 16Mbps Token Ring networks.	20 MHz
Category 5	data grade	Used for 100BaseTX Fast Ethernet, SONET, and OC-3 ATM networks.	100 MHz
Category 5e	data grade	Designed to support Gigabit (1000Mbps) Ethernet.	100 MHz
Category 6	data grade	Also utilized for Gigabit (1000Mbps) Ethernet, with improved performance and headroom.	250 MHz
Category 6A	data grade	Specified for both Gigabit (1000Mbps) and 10 Gigabit Ethernet applications.	500 MHz

 

 

Standard horizontal UTP cable is comprised of four pairs. A standardized color code is used to identify each pair and its individual conductors. One conductor in the pair is designated with a solid color, while the other is a white insulator with a stripe of the pair's color. The color code for a standard four-pair cable is defined in the table below.

 

 

Wire Number	Pair Number	Color
1	1	white/blue
2	1	blue
3	2	white/orange
4	2	orange
5	3	white/green
6	3	green
7	4	white/brown
8	4	brown

 

UTP backbone cables, which contain a larger number of pairs, are organized around 25-pair binder groups. A systematic two-level color code is applied: one sequence is used to identify the binder groups themselves, and another is used to identify each pair within a group.

 

A standard 25-pair binder group is subdivided into five major color-coded groups, each containing five pairs:

 

White – pairs 1 to 5

Red – pairs 6 to 10

Black – pairs 11 to 15

Yellow – pairs 16 to 20

Violet – pairs 21 to 25

 

Within each of these five major groups, the individual pairs are distinguished by a secondary color code:

 

Blue – 1st pair

Orange – 2nd pair

Green – 3rd pair

Brown – 4th pair

Slate – 5th pair

 

The complete color code for a 25-pair binder group, which results from combining the major group color and the pair color, is systematically presented in the following table and is clearly depicted in the accompanying diagram.

 

Wire Number	Pair Number	Group Color Code	Pair Color Code	Color
1	1	white	blue	white/blue stripe
2	1			blue/white stripe
3	2		orange	white/orange stripe
4	2			orange/white stripe
5	3		green	white/green stripe
6	3			green/white stripe
7	4		brown	white/brown stripe
8	4			brown/white stripe
9	5		slate	white/slate stripe
10	5			slate/white stripe
11	6	red	blue	red/blue stripe
12	6			blue/red stripe
13	7		orange	red/orange stripe
14	7			orange/red stripe
15	8		green	red/green stripe
16	8			green/red stripe
17	9		brown	red/brown stripe
18	9			brown/red stripe
19	10		slate	red/slate stripe
20	10			slate/red stripe
21	11	black	blue	black/blue stripe
22	11			blue/black stripe
23	12		orange	black/orange stripe
24	12			orange/black stripe
25	13		green	black/green stripe
26	13			green/black stripe
27	14		brown	black/brown stripe
28	14			brown/black stripe
29	15		slate	black/slate stripe
30	15			slate/black stripe
31	16	yellow	blue	yellow/blue stripe
32	16			blue/yellow stripe
33	17		orange	yellow/orange stripe
34	17			orange/yellow stripe
35	18		green	yellow/green stripe
36	18			green/yellow stripe
37	19		brown	yellow/brown stripe
38	19			brown/yellow stripe
39	20		slate	yellow/slate stripe
40	20			slate/yellow stripe
41	21	violet	blue	violet/blue stripe
42	21			blue/violet stripe
43	22		orange	violet/orange stripe
44	22			orange/violet stripe
45	23		green	violet/green stripe
46	23			green/violet stripe
47	24		brown	violet/brown stripe
48	24			brown/violet stripe
49	25		slate	violet/slate stripe
50	25			slate/violet stripe

 

As shown clearly below

 

 

For UTP cables that contain more than 25 pairs, additional binder groups are color-coded by repeating the same sequence of major group colors in conjunction with a binder group identifier. The scheme for the first several binder groups is shown below.

 

Pair Count	Binder Group Color
1—25	White—blue
26—50	White—orange
51—75	White—green
76—100	White—brown
101—125	White—slate
126—150	Red–blue
151—175	Red—orange
176—200	Red—green
201—225	Red—brown
226—250	Red—Slate
251—275	Black—blue
276—300	Black—orange
301—325	Black—green
326—350	Black—brown
351—375	Black—slate
376—400	Yellow-blue

 

 

Four-pair UTP horizontal cables are terminated with an 8-position modular connector, commonly known as an RJ45 connector, at the work area outlet. The RJ45 jack is an 8-conductor modular interface that is engineered to match the specific performance requirements (Category 5e, 6, 6A, etc.) of the UTP cable being terminated, thereby ensuring that the channel's performance specifications are maintained.

 

When a jack or a patch panel is wired, one of two standardized wiring schemes is followed: T568A or T568B. These standards define the pin-pair assignments that are used for terminating the wires of UTP cable onto the pins of the 8P8C modular connectors. In UTP cable, each of the four pairs is represented by a specific color: Pair 1 is blue, Pair 2 is orange, Pair 3 is green, and Pair 4 is brown.

 

The fundamental difference between the two standards is that the positions of the orange and green pairs (pairs 2 and 3) are swapped. Both configurations are wired in a "straight-through" manner, meaning pin 1 is connected to pin 1, pin 2 to pin 2, and so on, across the cable. Either configuration can be used within a network installation; however, it is critically important that the same configuration is used consistently on both ends of a given cable run. Mixing the two standards on a single cable will result in a wiring error.

 

 

The pinout and color assignments for both T568A and T568B are detailed in the following chart.

 

Pin	T568A Pair	T568B Pair	Wire	T568A Color	T568B Color	Pins on plug face (socket is reversed)
1	3	2	tip	white/green stripe	white/orange stripe
2	3	2	ring	green solid	orange solid
3	2	3	tip	white/orange stripe	white/green stripe
4	1	1	ring	blue solid	blue solid
5	1	1	tip	white/blue stripe	white/blue stripe
6	2	3	ring	orange solid	green solid
7	4	4	tip	white/brown stripe	white/brown stripe
8	4	4	ring	brown solid	brown solid