Page 110 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Unit 6: Data Communication

Notes
6.8 Self-Assessment Questions
6.9 Review Questions

6.10 Further Reading

Objectives

After studying this unit, you will be able to:
 Discuss local and global reach of network

 Explain data communication with standard telephone lines
 Explain data communication with modems
 Understand data communication using digital data connections
 Explain wireless networks

Introduction

Data Communications is the transfer of data or information between a source and a receiver. The
source transmits the data and the receiver receives it. The actual generation of the information is
not part of Data Communications nor is the resulting action of the information at the receiver. Data
Communication is interested in the transfer of data, the method of transfer and the preservation
of the data during the transfer process.
In Local Area Networks, we are interested in “connectivity”, connecting computers together to
share resources. Even though the computers can have different disk operating systems, languages,
cabling and locations, they still can communicate to one another and share resources.

The purpose of Data Communications is to provide the rules and regulations that allow computers
with different disk operating systems, languages, cabling and locations to share resources. The
rules and regulations are called protocols and standards in Data Communications.

6.1 Local and Global Reach of the Network

Data transmission, digital transmission, or digital communications is the physical transfer of
data (a digital bit stream) over a point-to-point or point-to-multi-point communication channel.
Examples of such channels are copper wires, optical fibers, wireless communication channels, and
storage media. The data is represented as an electromagnetic signal, such as an electrical voltage,
radiowave, microwave, or infrared signal.
The messages are either represented by a sequence of pulses by means of a line code (baseband
transmission), or by a limited set of continuously varying wave forms (passband transmission),
using a digital modulation method. The passband modulation and corresponding
demodulation (also known as detection) is carried out by modem equipment. According to the
most common definition of digital signal, both baseband and passband signals representing
bit-streams are considered as digital transmission, while an alternative definition only
considers the baseband signal as digital, and passband transmission of digital data as a form
of digital-to-analog conversion.

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