Chapter 13: Data Communication

Data communication can be defined as communication between two computers. It contains
a sender, a receiver, and a communication channel. In real life data communication
process contains many hardware devices and software techniques which make it an extremely
complex process.
Definition
Data communication can be defined as the exchange of information between two
computers.
Characteristics of a Data communication
1. Correct delivery: - The sender transmits data to a receiver. It must reach only the
correct receiver.
2. Accurate delivery : - The data sent must be received in the same form
3. Timely delivery: - The data must travel form sender to receiver in a finite amount of
time.
ANALOG AND DIGITAL SIGNALS
Definition
An analog signal is a continuously varying signal (sinusoidal wave)
Digital Signal takes the form of pulses. It is not continuous

Frequency, Period, Amplitude and Phase of an analog signal.
Frequency is the number of cycles per second. i.e. It is the number of waves per second
measured in hertz (Hz).
Example: Intel Pentium Microprocessor with 2.5 GHz speed
Period: The time taken for a wave to complete a cycle is called period.
Amplitude: - Height of a signal form a horizontal axis
Phase: The phase of a signal is related to the position of a wave relative to time and is
measured in degrees.

DATA COMMUNICATION EQUIPMENTS

1. MODEM (MODulator DEModuator)
Modem stands for modulator demodulator. A modulator converts analog signal to digital (this process is called Modulation) and demodulator converts digital signal to analog (this process is called demodulation).
Example: BSNL Modem for Broad band Connection in our home, office, school etc.
2.BRIDGE
It is used to link to net works. It is used to connect same type of networks (LAN Local Area
Networks).
3.ROUTER
A router is similar in operation to a bridge. But it can connect two networks with different protocols. it joins two networks and routes the data from one place to another place.

4.GATEWAY
It is a communication device that is used to connect two networks of different types.(LAN
and WAN)
5.REPEATER
Repeater is a communication device which receives, amplifies and transmits the signals in
both directions.

6.MULTIPLEXER
Multiplexer divides the physical lines into different channels. Multiplexer combines the
inputs from different sources and loads them into different channels. The combined signals
are separated by a device called de multiplexer.

 Def :-Attenuation
The degradation of signal strength while traveling through a medium