Communications and Networks

Chapter 6

Objectives• Defines the components required for

successful communications• Describe uses of communications• Identify the various types of transmission

media• Explain the purpose of communications

software• Describe commonly used communication

devices

Objectives• Explain the difference between a LAN and

a WAN• Understand the various communications

protocols• Identify the intranets and extranets

What is communication?

Communication•  is the activity of conveying information

through the exchange of ideas, feelings, intentions, attitudes, expectations, perceptions or commands, as by speech, non-verbal gestures, writings, behavior and possibly by other means such as electromagnetic, chemical or physical phenomena. It is the meaningful exchange of information between two or more participants (machines, organisms or their parts)

Communication• the act or process of using words, sounds,

signs, or behaviors to express or exchange information or to express your ideas, thoughts, feelings, etc., to someone else

– Merriam-Webster.com

Communication

• A process in which one computer transfers data, instructions, and information to another computer(s).

– IT111 Computers and Information Processing

Requirements for Communication:

1. Sending Device – a device that initiates the transfer

2. Modem – a communications device that converts the sent material into signals capable of being carried by a communications channel.

Requirements for Communication:

3. Communications channel- over which signals are sent

4. Communications Device- receives the signals and converts them into a form understood by the receiving device

Requirements for Communication:

5. Receiving Device – a device that accepts the sent material

How Communications

Used?

Electronic Mail is the exchange of text messages and computer files via a communications network.

Voice Mail - functions like an answering machine but converts an analog voice message into digital form.

Fax (Facsimile) machine sends and receives documents via telephone lines.

Telecommuting – allows employees to work away from the standard workplace and communicate using some communications technology.

Videoconferencing – involves using video and computer technology to conduct a meeting between participants at two or more geographically separate locations.

Groupware – is a software application that helps people work together and share information over a network

Electronic Bulletin Board System – is a computer that maintain a centralized collection of electronic messages.

Global Positioning System (GPS) consists of earth-based receivers that analyze satellite signals to determine the receiver’s geographic location.

Internet – a worldwide collection of networks, offers the World Wide Web and such popular Web-based activities as e-commerce and Internet telephony.

Channel

which is the communications path between two devices.

Communications Channel

Is composed of one or more transmission media.

Transmission Media

Consists of materials or techniques capable of carrying one or more signals

Types of Transmission Media:

• Physical Transmission Media– Use wire, cable and other tangible (touchable)

materials to send communications signals• Wireless Transmission Media

– Send communications signals through air or space using radio, microwave, and infrared signals

Physical Transmission

Media

Twisted Pair Cable• Consists of one or more twisted-pair wires

bundled together. • Each Twisted-pair wire consists of two

separate insulated copper wires that are twisted together.

• The wires are twisted together to reduce noise

• Noise- is an electrical disturbance that can degrade communications.

• Shielded Twisted Pair (STP) Cable- has a metal wrapper around each twisted-pair wire, which further reduces noise. Use in environments susceptible to noise such as in LAN.

• Unshielded Twisted Pair Cable – Inexpensive and easy-to-install, commonly are used in telephone networks

Coaxial Cable• Consists of a single copper wire surrounded

by three layers:– Insulating material– Woven or braided metal– Plastic outer coating

• Used in cable television wiring because it can be cabled over longer distances

• Is also insulated more than twisted pair cable, and thus is not as susceptible to noise.

Coaxial Cable

Fiber Optic Cable• Consists of dozens or hundreds of thin

strands of glass or plastic that use light to transmit signals.

• Optical Fiber – each strand– Is as thin as a human hair.

• Inside the Fiber Optic Cable, an insulating glass cladding and a protective coating surround each optical fiber

Fiber Optic Cable• Advantages

– Capable of carrying more signals than other wire cables

– Faster data transmission– Less susceptible to noise (interference) from

other devices – Better security signals during transmission – Smaller size (much thinner and lighter weight)

Fiber Optic Cable• Disadvantages

– Expensive – Difficult to install and modify– Requires more protection around the cable

Fiber Optic Cable

Wireless Transmission Media

Broadcast Radio

• Is a wireless transmission medium that distributes radio signals through the air over long distances such as between cities, regions, and countries.

Broadcast Radio• For radio transmission:

– Transmitter- to send the broadcast radio signal

– Receiver – to accept it

To receive the broadcast radio signal, the receiver has an antenna that is located in the range of the signal.

Some networks use a transceiver, which both sends and receives signals from wireless devices.

Broadcast Radio• Examples:

– Listening to AM and FM radio stations– Watching TV stations – Talking on a citizens band (CB) radio– Support mobile communications to network

Broadcast Radio• Bluetooth

Geo

ICO

Odyssey