Communication channels and transmission media

• A communication channel is simply a medium through which a message is transmitted to its intended audience, such as print meida or broadcast (electronic) media.

• Transmission media describes the types of physical system used to carry a communication signal from one system to another.

• These can be Physical or Wireless

Physical transmission media

• These include wires, cables and any other tangible (touchable) materials used to send communication signals.

• These include;

1 – Twisted Pair cablesA type of cable that has two independently insulated wires twisted around each other.

The oldest, simplest, andmost common type of conducted media is twisted pair wires. Twisted pair cable comes in two varieties: Shielded and Unshielded Twisted Pair (UTP).

Unshielded twisted cable (UTP)• These are the most

popular type of cable around the world.

• They come in 6 different types, and depending on what you want to achieve, you will need to employee the appropriate type of cable.

Applicability• Generally used as phone

cables

UTP (UNSHIELDED TWISTED CABLE)

• UTP Note:• Inexpensive• Can be affected by

interference as there is no protective metal shield

Shielded twisted pair (STPs)

Note:• They are more expensive

compared to UTPs• Can’t be affected by

interference as they have a protective metal shield

A device known as a Registered Jack (RJ) connectors are used to interface between UTP and the interface cards of a computer.

RJ-45 is an 8-position connector used for network cabling usually on Ethernet connections.Twisted pair cables have data transfer rates ranging from 10Mbps 1 Gigabyte.

• generally speaking, the advantages of STP cables include;

1. They are Cheap

2. Easily available on market

3. small in size

4. easy to install

It is the most popular and generally the best for schools.

Coaxial Cables• COAXIAL CABLE • A CABLE that consist of two conductors

that share a common axis. The inner conductor is made up of a solid copper wire (called a core) surrounded by an insulator, or a metal shield.

• The core, which actually transports the data, consists of a single copper strand or of several braided strands.

• The insulator surrounding the central core is made of a dielectric material that prevents any contact with the shield that could cause electrical interactions (short circuit).

Because of its good shielding properties, coaxial cable is very good at carrying analog signals with a wide range of frequencies. Coaxial cables are used to carry radio, video, measurement and data signals.

• Coaxial cable also comes in two primary physical types:

(a) thin coaxial cable (that come in a diameter of 0.25 inches and are used to connect workstations in the same office)

(b) thick coaxial cable (come with a diameter of 0.5 inches and are used to interconnect workstations in different rooms)

BNC connectors are used to connect coaxial cables on the network

BNC refers to Bayonne – Neill Councilman

• BNC Connector

• These connectors are mostly used in networks and video connections were shielding against electromagnetic interference is important

Advantages of using Coaxial Cables as a Transmission Medium

1. Versatility

Coaxial cables can be used for a number of different functions. When you hook up your DVD player to your television, you may use a coaxial cable.

These cables are also often used to connectYour television or computer to a satellite dish or cable connection. Coaxial cables are capable of carrying anything from radio transmissions to video to data signals.

2. Capacity

Because Coaxial cables are capable of transmitting so many different types of signals, their capacity is important.

These cables consist of a large number of copper wires that are banded together within the rubber outer coating of the cable. These cables are capable of transmitting large amounts of data at a high rate of speed, up to 100 megabytes per second.

This makes a coaxial cable the ideal type to use for broadband Internet connection, as well as television service to avoid a delay.

3 – Frequency Range

Different kinds of data require various frequencies to transmit the information from one place to another.

Coaxial cables are capable of transmitting various frequencies, even at the same time, making the cables a good choice for running multiple connections on the same line, such as both Internet and cable through the same line.

4- Protection

Coaxial cables are typically protected by thick layers of rubber. This not only protects the delicate wires inside from breaking or starting a fire; it also helps to keep outside interference from the wires.

The lack of interference means that the cables are able to transmit information more quickly and efficiently. It also creates a low occurrence of errors in the data that istransmitted through the cable. The signal is also capableof travelling over longer distances when encased within a coaxial cable.

DISADVANTAGES OOF USING COAXIAL CABLES

1. Heavy and bulky to carry

2. More expensive compared to the Twisted Pair Cable to buy

3. Difficult to work (difficult to install….. The more complex the network, the more difficult to use)

FIBRE OPTIC CABLES• It’s a network cable that contains strands

of glass fibre inside an insulated casing.

• It consists of a centre glass core surrounded by several layers of protective materials. They are designed to carry data for long distances and at very high bandwidth (gigabit speed)

• They carry communications signals

using pulses of light rather than electronic

signals (thereby eliminating the problem of electrical interference)

Advantages of Fibre Optic Cables• Carry significantly more signals than other cables.

• Faster data transmission (because of no external & internal noise)

• Early detection of cable damage and secure transmission• Secure data transfers since data is sent as beams of

light.

• Not affected by electromagnetic interference, crosstalk and radio frequencies

• Better security for signals during transmission.

• Since it carries no electrical signals, these cables can be used to connect buildings with different electrical grounds.

Disadvantages of Optical Fibre Cables1. Expensive as compared to other media• Buying and installation

2. Harder to install and modify. • Special equipment required

3. Physical Damage

THINK!!! HAVE YOU SEEN FIBRE OPTIC CABLES BEING INSTALLED?