This is the summary notes of the important terms and concepts in Chapter 21 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
INTRODUCTION TO DATA
COMMUNICATIONS AND NETWORKING
Information that is stored in digital form. Information that
has been processed organized and stored.
Knowledge or intelligence.
The transmission, reception, and processing of digital
It is to transfer digital information from one place to
Data Communications Circuit
A set of devices interconnected by media links.
Systems of interrelated computers and computer equipment and
can be as simple as a personal computer connected together through the PTN.
Data Communications Networks
Automatic teller machine
When was one of the earliest means of communicating
electrically coded information occurred?
In 1833, he developed an unusual system based on a
five-by-five matrix representing 25 letters. The idea was to send message
over a single wire.
Carl Friedrich Gauss
The first successful data communications that was invented in
1832. Dots and Dashes.
He invented the first practical data communications code which
is called Morse Code.
Samuel F.B. Morse
Allegedly invented the first telegraph in England.
1. Sir Charles Wheatstone
2. Sir William Cooke
In 1874, he invented the telegraph multiplexer which Emile
allowed up to six different telegraph machines to be transmitted
simultaneously over a single wire.
It was invented in 1875 by Alexander Graham Bell.
He succeeded in sending radio telegraph messages.
The only means of sending information across large spans of
water until 1920.
A German engineer, demonstrated a computing machine sometime
in the late 1930s.
Developed the ENIAC computer on Feb. 14, 1946
J. Presper Eckert
A technique that process one job at a time.
Built in 1951 by Remington Rand Corp., was the First
mass-produced electronic computer.
A public data communications network used by millions of
people all over the world to exchange business and personal information.
Private data communications networks used by many companies to
exchange information among employees and resources.
Any system of computers, computer terminals or computer
peripheral equipment used to transmit and receive information between two or more
Data Communications Network
A set of equipment, transmission media and procedures that
ensures that a specific sequence of events occurs in a network in the proper
order to produce the intended results.
Messages are intended for all subscribers on the network.
Messages are intended for a specific group of subscribers.
Defines the procedures that the systems involved in the
communications process will use.
Sets of rules governing the orderly exchange of data within
the network or a portion of the network.
Data Communications Protocols
The list of the protocols used by a system.
It consists of two or more independent levels.
A logical connection is established between the endpoints
prior to the transmission of data.
Connection Oriented or Connectionless
They are designed to provide a high degree of reliability for
data moving through the network.
A connection process that occurs between two stations before
any data are actually transmitted.
It refers to the structure or format of the data within the
message, which includes the sequence in which the data are sent.
Guidelines that have been generally accepted by the data
Types of standards:
Ø Proprietary system -open
Ø open system
Data Communications Standards
Generally controlled and manufactured by one company.
The international organization for standardization on a wide
range of subjects.
The member of ISO from the United States.
American National Standard Institute
It is formerly CCITT, one of four permanent parts is based in
International Telecommunications Union
Modem interfaces and data transmission over the telephone
Data transmission over public digital Network, e-mail and
An international professional organization founded in the
United States and is comprised of electronics, computer and communications
Institute of Electrical & IEEE)and
A non-profit U.S. trade association that establishes and
recommends industrial standards.
Electronics Industry Association
The leading trade association in the communications and
information technology industry.
Telecommunications Industry Association
The research arm of the Department of Defense in 1957.
Advanced Research Projects Agency
A large international community of network designers,
operators, vendors and researches concerned with the evolution of the
internet architecture and the smooth operation of the internet.
Internet Engineering Task Force
It promotes research of importance to the evolution of the
future Internet by creating focused, long term and small research groups
working on topics related to internet protocols.
Internet Research Task Force
A unit of data.
Protocol data Unit
The process of adding and removing the PDU information.
It means to place in a capsule or other protected environment.
It means to remove from a capsule or other protected
Defines which entity the service is intended.
Service Access Point
The name for the set of standards for communicating among
Seven OSI layers:
Open Systems Interconnection
Responsible for the actual propagation of unstructured data
bits through a transmission medium.
Responsible for providing error-free communications across the
physical link connecting primary and secondary stations within a network.
Data Link Layer
Provides details that enable data to be routed between devices
in an environment using multiple networks, subnetwork, or both.
Controls and ensures the end-to-end integrity of the data
message propagated through the network between two devices, which provides
reliable, transparent transfer of data between two endpoints.
Responsible for network availability.
Provides independence to the application processes by
addressing any code or syntax conversion necessary to present the data to the
network in a common communications format.
It provides distributed information services and controls the
sequence of activities within an application.
An endpoint where subscribers gain access to the circuit.
Another term of station which is the location of computers,
computer terminals, workstations and other digital computing equipment.
Interconnects digital computer equipment.
Provides means to enter data from humans.
Encodes a wireless radio system without being converted to
Carries the encoded signals from the transmitter to the
Converts the encoded signals received from the transmission
medium back to their original form.
It could be a mainframe computer, personal computer
workstation or virtually any piece of digital equipment.
A type of transmission where all four bits can be transmitted
simultaneously during the time of a single clock pulse.
Parallel by Bit or Serial by Character
Transmission where four clock pulses are required to transmit
the entire four-bit code.
Serial by Bit
It involves only two locations or stations
It involves three or more stations.
Data transmission is unidirectional where information can be
sent in only one direction.
Also called Receive-Only, Transmit Only or One-way-only Lines
Data transmission is possible in both directions but not at
the same time.
way alternate lines
Transmissions are possible in both directions between two
stations simultaneously, but they must be between same time.
Transmission is possible in both directions at the same time
but not between the same two stations. It is possible only on multipoint
The process of sharing resources between computers over a data
The manual technique of moving data on disks.
Computers that hold shared files, programs and the network
Computers that access and use the network and shared network
The facilities used to interconnect computers in a network.
Data that file servers provide to clients.
Hardware resources provided to the users of the network by
Shared Printers and
An expansion card and prepares and sends data, receives data
and controls data flow between the computer and the network.
Network Interface Card
Allows personal computers to access files, print to a local
printer and have and use one or more disk and CD drives that are located on
Local Operating System
A program that runs on computers and servers that allows the
computers to communicate over a network.
One in which all computers share their resources.
Peer – to – Peer Client/
One computer is designated the server and the rest of the
computers are clients.
Dedicated Client/Server Network
Describes the layout or appearance of a network.
Describes how the network is actually laid out.
Describes how data actually flow through the network.
A multipoint data communications network where remote stations
are connected by cable segments directly to a central located computer.
A multipoint data communications circuit that makes it
relatively simple to control data flow between and among the computers.
A multipoint data communications network where all stations
are interconnected in tandem to form a closed loop or circle.
Every station has a direct two-point communications link to
every other station on the circuit.
Combining two or more of the traditional topologies to form a
larger, more complex topology.
Privately own networks in which 10 to 40 compute share data
resources with one or more file server.
Local Area Networks
A high-speed network similar to a LAN except the are designed
to encompass larger areas, usually that of an entire city.
Metropolitan Area Networks
Provides low-speed, long distance transmission of data voice,
and video information over large and widely dispersed geographical areas such
as country or an entire continent. It interconnects cities or states.
Wide Area Network
Bit rate of WANs.
1.5 Mbps-2.4 Gbps
Provides connects between countries around the entire globe.
Global Area Network
A network connection that normally carries traffic between
departmental LANs within a single company.
A network connection used to carry traffic to and from LANs
located in various buildings on campus.
Developed by Department of Defense, comprise of several
interactive modules that provide specific functionality.
TCP/IP Protocol Suite
The network layer of TCP/IP.
Internet work Layer
Transport layer of TCP/IP.
Transmission Control Protocol
User datagram Protocol
Provides a means of physically delivering data packets using
frames or cells.
Network Access Layer
Contains information that pertains to how data can be routed
through the network.
Services the process and internet layers to handle the
reliability and session aspects of data transmission.
Provides applications support.
Defines a three layer logical hierarchy that specifies where
things belong, how they fit together and what functions go where.
Cisco Three-Layer Model
The core of the network as it resides at the top of the
hierarchy and is responsible for transporting large amounts of data traffic
reliably and quickly.
The communications point between the access and the core layer
that provides routing, filtering, WAN access and how data packets are allowed
to access the core layer.
Another term for Distribution layer.
Controls workgroup and individual user access to
Another term for Access layer.