The document discusses datacom circuits and networks, covering components such as sources, transmitters, receivers, and transmission media. It describes different transmission types (serial and parallel), circuit arrangements (point-to-point and multipoint), and network models (peer-to-peer and dedicated client/server). Additionally, it outlines network topologies, classifications, and comparisons of LAN, MAN, WAN, and GAN based on size, speed, and geographical coverage.

1. Module 3
Datacom Circuits, Circuit
Arrangements, and Networks
Chapter 21
Electronic Communications Sytems , Fifth Editon
By: Wayne Tomasi
ECE @Saint Louis University, Baguio City 1
Prepared by: Engr. Jeffrey Des B. Binwag

2. Datacom Circuit Components
• Source
• Transmitter
• Transmission Medium
• Receiver
• Destination
ECE @Saint Louis University, Baguio City 2

3. Serial and Parallel Data Transmission
• Parallel Transmission. Involves sending data
bits simultaneously on a set of transmission
lines on a single clock pulse. Also called
parallel by bit or serial by character
transmission.
• Serial Transmission. Involves sending data
bits on a single transmission line involving
several clock cycles. Also called serial by bit
transmission.
ECE @Saint Louis University, Baguio City 3

4. Datacom Circuit Arrangements
• Circuit Configurations.
– Point-to-point. Involves only two stations on a circuit.
– Multipoint. Involves more than two stations in a datacom
circuit.
• Transmission Modes.
– Simplex (SX). Transmit only or receive only or one-way-
only lines
– Half duplex (HDX). Two way alternate or either-way lines.
– Full duplex (FDX). Two-way simultaneous or both-way
lines
– Full/full duplex (F/FDX). Transmission in both directions at
the same time but not between the same two stations.
ECE @Saint Louis University, Baguio City 4

5. Datacom Network Components,
Functions and Features
• Servers. Computers that hold shared files,
programs, and the network operating system.
• Clients. Computers that access and use the
network and other shared resources.
• Transmission Media. Facilities used to
interconnect computers in a network.
• Shared Data. Data that file servers provide to
clients such as data files, printer access programs,
and e-mail.
ECE @Saint Louis University, Baguio City 5

6. Datacom Network Components,
Functions and Features
• Shared Peripherals. Hardware resources provided to users by
the network servers.
• Network Interface Card (NIC). Prepares, and sends data,
receives data, and controls data flow between the computer
and the network.
• Local Operating System (LOS). A software that allows
personal computers to access files, print to a local printer, and
connect to other local memory and peripheral devices.
• Network Operating System (NOS). A program that runs on
computers and servers that allows the computers to
communicate over the network.
ECE @Saint Louis University, Baguio City 6

7. Datacom Network Models
• Peer-to-Peer Client/Server. A network in which
all computers share their resources, such as hard
drives, printers, and so on, with all the other
computers in the network.
– No dedicated servers or hierarchy among computers
– Used for networks with 10 users or less, when
computers are located in the same general area, when
security is not an issue, or when limited growth is
projected for the network in the immediate future.
ECE @Saint Louis University, Baguio City 7

8. Datacom Network Models
• Dedicated Client/Server. A network where one
computer is designated as the server, and the rest
of the computers are clients.
– Features highly centralized network control
– There could be a dedicated server to serve each
network function.
– Preferred model for general purpose data networks.
ECE @Saint Louis University, Baguio City 8

9. Datacom Network Topologies
• Network Topology. Describes the layout or appearance
of a network. A physical topology describes how a
network is actually laid out while the logical topology
describes how data actually flow through the network.
– Star. A multipoint datacom network where remote stations are
connected by cable segments directly to a centrally located
computer called a hub which acts as a multipoint connector.
– Bus. A multipoint datacom circuit where remote stations are
physically or logically connected to a single transmission line
called a bus. Also called a multidrop, horizontal bus, or linear
bus, it is the simplest and most common method of
interconnecting computers.
ECE @Saint Louis University, Baguio City 9

10. Datacom Network Topologies
– Ring. A network where all stations are interconnected in tandem
(series) to form a closed loop or circle. In this type of topology
that is also called a loop, transmissions are unidirectional and
must propagate through all stations in the loop such that each
computer acts like a repeater.
– Mesh. A network where every station has a direct two-point
communication link with the rest of the computers in the
network. Also known as a fully connected network, this topology
offers reduced traffic problems, increased reliability, and
enhanced security although requires a much greater number of
transmission paths and input/output ports.
– Hybrid. A network that combines two or more of the traditional
topologies to form a larger, more complex topology.
ECE @Saint Louis University, Baguio City 10

11. Datacom Network Classifications
• Network Classification. Generally classified by size, which
includes geographic area, distance between stations, number
of computers, transmission speed, transmission media, and
the network’s physical architecture.
– LAN (Local Area Network). Typically privately owned data
communications networks in which 10 to 40 computer users share
data resources with one another. Most LANs are owned by the
company or organization that uses it and have a connection to a
building backbone for access to other LANs, MANs, WANs, and GANs.
– MAN (Metropolitan Area Network). A high speed network similar to
a LAN except it is designed to encompass larger areas, usually an
entire city/metropolis. A MAN can be owned and operated entirely
by a single company, or could lease services and facilities on a
monthly basis from the local cable or telephone company.
ECE @Saint Louis University, Baguio City 11

12. Datacom Network Classifications
– WAN (Wide Area Network). The oldest type of data communications
network that provides relatively slow-speed, long-distance
transmission of data, voice, and video information over relatively large
and widely dispersed geographical areas, such as a country or an entire
continent.
– GAN (Global Area Network). A network that provides connections
between countries around the entire globe.
– Building Backbone. A network connection that normally carries traffic
between departmental LANs within a single company.
– Campus Backbone. A network connection used to carry traffic to and
from LANs located in various buildings on a campus or similar settings
like corporate headquarters, universities, airports, and research parks.
– Enterprise Network. A network connection that includes some or all
of the previously mentioned networks and components connected in a
cohesive and manageable fashion.
ECE @Saint Louis University, Baguio City 12

13. Datacom Networks Comparison
ECE @Saint Louis University, Baguio City 13
Network
Classification
Geographic Area Distance
Between
Stations
Transmission
Speed
Examples
LAN Same room,
building, or
building complex
A few miles 10 – 100 Mbps PAN,
Ad-hoc wireless,
SoHo
MAN City, Metropolis A few hundred
miles
1.5 – 10 Mbps SMDS, FDDI,
ATM
WAN Country,
Continent
100 to 1000
miles
1.5 Mbps –
2.4 Gbps
ISDN, X.25, ATM,
T1 and T3 Digital
Carrier Systems
GAN Global Thousands of
miles
1.5 Mbps –
100 Gbps
Internet, WWW