Data communication involves the exchange of data between devices via a transmission medium. It has five key components: a message, sender, receiver, medium, and protocol. There are three main modes of data communication: simplex, half duplex, and full duplex. Guided media like twisted pair cables, coaxial cables, and fiber optic cables provide a physical channel for transmission, while unguided media like radio waves, microwaves, and infrared transmit electromagnetic waves without a physical medium.

1. Data Communication is
the exchange of data
between two devices via
some form of
transmission medium
such as a wire cable

2. Here are three fundamental characteristics
of Data Communication:
1. Delivery to correct destination
2. Accuracy of data
3. Timelines Timely delivery of data

3. A data communication system has five
components:
1. Message
2. Sender
3. Receiver
4. Medium
5. Protocol

4. There are three modes for data
communication:
1. Simplex
2. Half Duplex
3. Full Duplex

5. In Simplex mode, the communication is
unidirectional. For example:
1. Keyboard
2. Monitor
3. Television etc.

6. In Half Duplex mode, each station can both
transmit and receive data but not at the
same time, e.g. :
1. Walkie-talkie
2. Radio phones in Police cars etc

7. In Full Duplex mode, both station can
transmit and receive data simultaneously,
e.g. :
1. Telephone Network
2. 2-Way Traffic etc.

8. Guided Media:
Which provide a physical channel from one
device to another:
• Twisted Pair Cable
• Coaxial Cable
• Fiber Optic Cable

9. Un-Guided Media:
Transports electromagnetic waves without
using a physical medium:
• Radio Waves
• Microwaves
• Infrared

10. Least expensive and most widely used. A
twisted pair consists of two conductors, each
with its own plastic insulation, twisted
together.

11. A conductive metal such as copper transmits
data using electric current. Many twisted
pairs can occur in a single cable. They tend
to have different twist length to prevent
crosstalk interference. Most common within
telephone networks and data networks.

12. Distance:
Analog : 5 to 6 Kms then amplifiers
required.
Digital : 2 to 3 Kms then repeaters required.

13. Two types of Twisted Pair Cable:
1. UTP – Unshielded Twisted Pair
2. STP – Shielded Twisted Pair

14. Versatile transmission medium that operates
over a wide range of frequencies.

15. Used in:
• Cable Television Network
• Old Local Area Networks
• Long Distance Telephone
Transmission

16. A fiber optic cable is made of
glass and transmits signals in
the form of light. Data
transmission using optical fiber
is many times faster than with
electrical method

17. It has following characteristics:
• Light wave.
• High transmission rate.
• Immune to interference.
• Light weight.
• Greater repeater spacing.

18. Radio waves are omni-directional. When an
antenna transmits radio waves, they are
propagated in all directions. They can
propagate in the sky mode and can travel
long distance.

19. Used for:
• Radio
• Television
• Cordless Phones
• Paging Systems

20. Microwaves are unidirectional. When an
antenna transmits microwave waves, they
van be narrowly focused i.e. sending and
receiving antennas need to be aligned.
Microwave propagation is line-of-sight.
Repeaters are oftenly needed for long
distance communication.

21. Used for:
• Cellular Phones
• Satellite Networks
• Wireless LANs

22. Infrared transmission is usually
limited to a small area, e.g. one
room, with the transmitter pointed
towards the receiver. The hardware
is inexpensive and does not require
an antenna. Infrared signal can not
penetrate walls.

23. We cannot use infrared waves
outside a building because the sun’s
rays contain infrared waves that can
interfere with the communication.
Infrared signals can be used for
short range communication e.g.
mobile phones, remote controls etc.