Lec1_Intro to Data Comm

8/2/2019 Lec1_Intro to Data Comm

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ITC35 - Data Communication and Connectivity 1/4

Lec 1 Data Communication Noli M.. Argente

Telecommunications general term for the electronic transmission of information of any type

including television pictures, sounds, facsimiles, and data in the form of electronic signals or impulses,sent either as an individual message between two parties or as a broadcast to be received at many

locations.

It could also be referred to as communications over a distance using technology to overcome

that distance.

The messages can be sent from one sender to a single receiver (point-to-point) or from one

sender to many receivers (point-to-multipoint).

DATA COMMUNICATIONS

Is the process of transferring digital information (usually in binary form) between two or morepoints. Information is defined as knowledge or intelligence.

Is the process of communicating information in binary form between two points. It issometimes called computer communications because most of the information interchange

today is between computers, or between computers and their terminals, printers or otherperipheral devices.

Involves data transfer from one computer to another through a communications medium such

as telephone, a microwave relay, or satellite link or a physical cable.

Three Components:

1. Transmitter also called the source

A transmitter can be any circuit or electronic device designed to send electronically encoded

data to another location.

2. Transmission path or channel

a path or a link through which information passes between two devices. In communications, amedium for transferring information also known as a line or a circuit. A communications channel can

carry information in many forms such as data, sound and/or video in either digital or analog form.

3. Receiver also called the sink

a receiver could be any device designed to receive any conveyed message from the transmitter

or the source.

ELECTRONIC TRANSMISSION

is the transmission, reception , and processing of information with the use of electronic circuits.

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Universal Seven-Part Circuit of Data Communications System

1. The Data Terminal Equipment (DTE) at point A.2. The interface between the DTE and the Data Circuit-terminating Equipment (DCE) or often

called Data Communications Equipment at point A.

3. The DCE at point A4. The transmission channel between point A and point B

5. The DCE at point B

6. The DCE-DTE interface at point B7. The DTE at point B

Point A Point B

Transmission Channel

DTE/DCE Interface DCE/DTE Interface

(a) BLOCK DIAGRAM

MODEM

is the contraction of the words MOdulator/DEModulator which converts digital signals coming

from a computer into their equivalent analog signals transmissible over telephone lines or viceversa.

Modulation - is the process of converting digital signals coming from a computer into their

equivalent analog signals transmissible over telephone lines or vice versa.

Data Communications Applications

Transfer of data between two or more PCs Ability to access remote programs or files through a global network called the Internet

Electronic Mails

Videoconferencing/Teleconferencing

Access to remote programs Access to remote databases

Enhanced communication facilities

Electronic Bulletin Board System

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DTE DCE DTEDCE


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Batch Processing data are accumulated over a period of time then processed periodically

Gathering source documents originated by business transactions such as sales orders or invoice

into groups called BATCHES. Recording transaction data on an input medium such as magnetic disks or magnetic tapes

Sorting the transactions in a transaction file into the same sequence as the record in a

sequential master file.

Computer processing that result in an updated master file in a variety of documents and reports

Online System or real-time processing systems process data immediately after they generated

and can provide immediate output to users

In full-pledged real-time processing system, data are processed as soon as they are originated

or recorded without waiting to accumulate batches of data. Data are fed directly into the computer system from online terminals without having to be

sorted and are always stored online in direct access files.

The masters files are always up-to-date since they are updated whenever data are originated,

regardless of its frequency.

Responses to users inquiry are immediate, since information in the direct access files can beretrieved almost instantaneously.

Major Differences between Batch Processing & Real-Time Processing

Characteristics Batch Processing Real-Time Processing

Processing of

Transactions

Transaction data is

recorded, accumulated intobatches, sorted and process

periodically

Transaction data is processed as

generated

File Update When batch is processed When transaction is processed

Response Time/

Turnaround Time

Several hours or days after

batches are submitted forprocessing

A few seconds after each

transaction is captured

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Data Communication Standards

Are simply a set of rules that were established for use in the computer industry by the

various international bodies

ISO International Standards Organization

IEEE Institute of Electrical and Electronics Engineers

ANSI American National Standards Institute

CLOSED SYSTEMS vs. OPEN SYSTEMS

Closed Systems

A term used to describe any computer design whose specifications are not

freely available. Such proprietary specifications make it difficult or impossiblefor third party vendors to create ancillary devices that worked correctly with a

closed-architecture machine

Closed systems resulted in the proliferation of proprietary systems where only

products coming form the same manufacturers could work

Open Systems

A term used to describe any computer or peripheral design that has publishedspecifications. It is designed to incorporate all devices----regardless of

manufacturer or model that can use the same communications facilities and

protocols

Open systems enable equipment produced by one vendor to be used with

equipment from any vendor that complies with the standards

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Lec1_Intro to Data Comm

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