Principles 
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Essentials 
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Telecommunications and Networks  

Objectives 
1. Understand principles of digital communications 
2. Identify major communication media 
3. Define and explain networking terms such as  

Protocols 
Media 
Architecture 
4. Explain the impact of telecommunications on an organization 

Telecommunications in Business 

 Defined as communications over a distance.  
– Telephone 
– Fax 
– E-mail 
 Reduces need for centralized data storage. 

Impact 

Improved communication 
– Increased quality 
Increased efficiency 
– Decreased cost 
 More effective distribution of data 
– Increased utilization 

Data Communications 

Any transfer of data within a computer or between a computer and another device. 
Data may represent any media 
– Voice 
– Video 
– Animation 
– Text 

Data Communications 

Also defined as the transmission and reception of digitized data, represented in binary code. 
– Parallel transmission 
– Serial transmission 
 
Packet Orientated 
– Messages are divided into informational units called packets. 
 
Protocols are the methods used to send packets through a medium 

Communication Modes 

 Simplex 
– One way 
Half-Duplex 
– Two way, but only one way at a time 
Duplex 
– Two way all the time 

Signal Timing 

When devices at both ends of the communication channel coordinate the timing of the signals, it is called synchronous communications. 
When data concerning the message  allowing the devices to coordinate their communications, it is called asynchronous communications. 

Asynchronous Transmission 

 Error correcting data can include parity bits as well as start and stop bits. 
 The extra data added to the original message is known as overhead. 

Communications Channel 

The physical medium through which data travels. 

Baseband and Broadband 

A channel that can carry a single message stream is called Baseband.  
A channel that can more than a single message stream is called broadband. 

Common Media 

Twisted Pair 
 Coaxial Cable 
 Microwave 
 Fiber 

Modems 

Modulate digital signals from computers onto analog signals that can travel over the phone company’s network. 
Demodulates the signals at the receiving end. 

Multiplexers 

At the sending end, combine several signals into a single stream that can be sent over a channel. 
At the receiving end, they separate, or demodulate, the same signals. 

Local Area Networks 

 A grouping of computing devices that can communicate. 
 May consist of a workgroup, a department, or similar group. 

Wide Area Networks 

A grouping of computing devices that can communicate that is spread over a wide geographic area. 
May consist of different company locations or similar groups. 
WANs typically use a common carrier to connect the different sites. 
A common carrier is any communications company that provides general access, dial up or dedicated, public telephone lines. 

Network Topology 

Star 
Ring 
Bus 

Protocols 

Protocol is the common method(s) that different computers use to communicate 
A protocol stack or suite is a complete set of protocols 

LAN Protocols and Architectures 

 Ethernet (contention) 
– 10 Megabit 
– 100 Megabit 
 Token Ring (token passing) 
– Active access methodology with advanced fault tolerance. 

ISO’s, OSI Network Model 

 Seven Layers 
– Application 
– Presentation 
– Session 
– Transport 
– Network 
– Data Link 
– Physical 

Switching Methods 

 Circuit Switching (dedicated channel) 
– Phone company 
Packet Switching (shared media) 
– Data Communications 

ISDN and ATM 

ISDN stands for Integrated Services Digital Network. 
– Digital Home Services 
ATM stands for Asynchronous Transfer mode. 
Digital Backbone Services 
– Backbone Services