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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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