cables in computer networks

CABLES AND THEIR CONNECTING STRUCTURES  IN COMPUTER NETWORK

Network Cable

Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size.

• Unshielded Twisted Pair (UTP) Cable
• Shielded Twisted Pair (STP) Cable
• Coaxial Cable
• Fiber Optic Cable

Twisted Pair Cable

Twisted pair cabling comes in two varieties: shielded and unshielded.

Unshielded Twisted Pair (UTP) Cable

A popular type of cable that consists of two unshielded wires twisted around each other. Due to its low cost, UTP cabling is used extensively for local-area networks (LANs) and telephone connections. It is the most popular and is generally the best option

Shielded Twisted Pair (STP) Cable

Although UTP cable is the least expensive cable, it may be susceptible to radio and electrical frequency interference (it should not be too close to electric motors, fluorescent lights, etc.). If you must place cable in environments with lots of potential interference, or if you must place cable in extremely sensitive environments that may be susceptible to the electrical current in the UTP, shielded twisted pair may be the solution. Shielded cables can also help to extend the maximum distance of the cables.

Coaxial Cable

Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.

Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial cabling are thick coaxial and thin coaxial.

Fiber Optic Cable

Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting.

Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. It is more difficult to install and modify.

CONCEPT OF STRAIGHT AND CROSS OVER CABLES

Straight Cable

A straight cable goes from a node to a device. A node is a computer or resource that attaches to a network.

Crossover Cable

A crossover cable goes from a device to an identical device, such as a router to another router, from a switch to another switch, or from a PC to another PC.

IDENTICATION OF STRAIGHT AND CROSS OVER CABLES

There are two standards adopted for Cabling EIA/TIA 568A & EIA/TIA 568B.

When you use single standard (either EIA/TIA 568A or EIA/TIA 568B) on both the end of cable then the resulting cable is STRAIGHT CABLE.

On the other hand if you use different cabling standard on the ends of cable then the resulting cable is CROSS CABLE

Making Straight Cable

Requirements: Two RJ45 Connectors, Crimping tool & Cable of desired length

Steps:

1. Remove the covering of CAT 5 cable.
2. Straighten the eight wires of the cable.
3. Using Crimping tool’s cutter cut the end of wires so that they are of same length.
4. Arrange the wire in order as shown in diagram

5. Insert the arranged cable in the RJ45 connector

6. In crimping tool insert the head of RJ45 connector and crimp (press) it
hardly.
7. Follow same step with same color order for the other end of cable too.
8. The wire you made by following these steps is a STRAIGHT cable.

Making Cross Cable

Steps 1 to 6 are same as for STRAIGHT through cables
7. Only difference is in color coding of other side of wire.
8. Wire that is on 1st number on A-side (one end) should be on 3rd number
on B-side (other side) & vice-versa.
9. Wire that is on 2st number on A-side (one end) should be on 6rd number
on B-side (other side) & vice versa.
10. Now Crimp the RJ45 connector.
11. Your CROSS wire is complete.