In a transmission system, it is called transmission medium to any type of hardware through which the sender and receiver establish communication. The transmission means are classified guided and unguided. In both cases the transmission takes place via electromagnetic waves. In the case of these waves means guided through lead wires.

The transmission speed, range and quality (absence of noise and interference) are the elements that characterize guided media. The evolution of technology in regard to cables has guided optimization of these three variables.

Transmission Speed: Currently achieved speeds differ considerably between different types of cables, the optical fiber being that which achieves a higher speed.

Signal range: Is determined by the attenuation suffered by the signal as is flowing through the wire and is greater the more distance to go, so this factor significantly limits the length of cable that can be installed without regenerating the signal.

Signal quality: One of the main problems transmiting a data stream through an electric cable consists of the magnetic field generated by the electrons circulation. This phenomenon is known as electromagnetic induction. The existence of a magnetic field around a wire will generate interference in nearby wires due to this same phenomenon.

Twisted Pair

The so called twisted pair cable consists of two insulated copper wires which are stranded helically, like a DNA molecule. Thus the twisted pair is a circuit that can transmit data.

It’s done this way because two parallel wires constitute a simple antenna. When the wires are twisted, electromgnetic inductived waves of different laps are canceled, so that the radiation of the cable is less effective. So braided shape reduces both external electrical interference as close pairs.

A twisted pair cable consists of a group of twisted pairs, usually four, coated by an insulating material.

Each of these pairs is identified by a color, the colors being assigned and groups of pairs as follows:

Par 1: White-Blue / Blue

Pair 2: White- Orange / Orange

Par 3: White-Green / Green

Par 4: White- Brown / Brown

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Twisted Pair Cable

The twisted pairs are usually shielded. According to the way this shielding is done we can distinguish various types of twisted pair cables, these are referred to by the acronym UTP, STP and FTP.

UTP is referred to as twisted pair cables unshielded. Being the simplest, do not have any conductive shield. Impedance is 100 omhs tipically, and is very sensitive to interference. The pairs are covered with a Teflon nonconductive mesh. This cable is quite flexible.

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UTP Cable
STP is the name for shielded twisted pair cables. Each pair is wrapped in a conductive mesh individually while another bigger one cover the pairs altogether. They have high noise immunity, but maximum rigidity.

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STP Cable

In the FTP, cable pairs are covered with a conductive mesh shaped overall braided. Thus, it improves the protection against interference, having an intermediate stiffness.

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FTP Cable

Depending on the number of pairs the in cable, the number of twisted turns per meter and materials used, structured cabling standards classify twisted pair cables by category: 1, 2, 3, 4, 5, 5e, 6 and 7. The last one is still being defined.

Category 3: supports transmission speeds up to 10 Mbits /sec. Used for voice telephony, 10Base-T Ethernet and Token ring to 4 Mbits /sec.

Category 4: supports speeds up to 16 Mbits /sec. It is accepted for Token Ring to 16 Mbits /sec.

Category 5: up to 100 Mbits /sec. Used for Ethernet 100Base-TX.

Category 5e: up to 622 Mbits /sec. Used for Gigabit Ethernet.

Category 6: supports speeds up to 1000 Mbits /sec.

 

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CAT6 UTP Cable

Twisted Pair cable must use RJ45 connectors to join the different elements that make up the network hardware. Until now only four out of the eight wires are used for data transmission. These are connected to the RJ45 connector pins as follows: 1, 2 (for transmission), 3 and 6 (to receive).

AWG stands for American Wire Gauge. It can appear in many catalogs classifying the types of cable. AWG refers to the thickness of the wires. When the thickness of the threads increases the AWG decreases. The telephone wire is used as a reference point; It has a thickness of 22 AWG. A 14 AWG wire thickness is thicker, and one 26AWG is thinner.

 

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