Digital data is usually
transmitted through an analog carrier signal by modulating one or more of the
carrier’s three characteristics i.e. amplitude, frequency and phase.
Modulator:
In electronic and communication, modulator is a device that converts data from
digital to analog signals at the transmitter side of a communication system.
Demodulator:
Demodulator works at the receiver side of the communication system and converts
analog signals to digital in order to regain the original digital data.
Modem:
Modem (modulator-demodulator)
is a hardware device that
performs both modulation and demodulation. Modem first
converts data into a format suitable for a transmission medium to
transfer it from one computer to another and demodulates signals at the receiver
end to decode the transmitted information. The purpose is to produce
a signal that can be transmitted easily and decoded reliably to
reproduce the original data.
Modulator: Converts from digital to analog signal
Demodulator – Converts from analog to digital signal
Modem – (Modulator/Demodulator) performs both the functions
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Router:
A router is a hardware device
that connects multiple networks (two LANs or WANs or a LAN and its ISP’s
network) and forward data packets along networks. Router
operates in network layer of OSI model and transmits data in the form
of packets. Routers are generally located at gateways, the places where two or
more networks connect.
Bridge:
In telecommunication networks,
a bridge is a product
that connects a local area network (LAN) to another Local Area Network (LAN) that uses
the same protocol. In other words, a bridge is a type of computer network device that provides interconnection with
other bridge networks that
use the same protocol. Bridge devices work at the data link
layer of the Open System Interconnect (OSI) model, connecting two
different networks together
and providing communication between them.
Switch:
A switch is a small hardware that connects devices on a computer network by
using packet switching to receive and forward data to the destination device. It
is basically a multiport bridge that uses MAC addresses to forward data at the
data link layer of the OSI model.
Hubs:
A hub is basically a multi-port repeater works on the Physical layer of OSI
model. A hub connects multiple wires coming from different branches, for
example, the connector in star topology which connects different stations. Hubs
cannot filter data, so data packets are sent to all connected devices. In
other words, collision domain of all hosts connected through Hub
remains one. Also, they do not have intelligence to find out best path
for data packets which leads to inefficiencies and wastage.
Repeater:
A repeater is an electronic device in a communication channel that receives a
signal, increases its power and retransmits it, allowing it to travel further so that the signal can cover
longer distances or be received on the other side of an obstruction. An
important point to be noted about repeaters is that they do not amplify the
signal. When the signal becomes weak, they copy the signal bit by bit and
regenerate it at the original strength by taking high input power and providing
low output power. Repeater is a 2 port device and operates under Physical
Layer.
Amplifier:
Amplifier is used for increasing
the amplitude or strength of the signal,
if the previously transmit signal is found weak. It uses electric power from
a power supply to increase the amplitude of a signal
applied to its input terminals, producing a proportionally greater amplitude
signal at its output.
Gateways:
A gateway is a piece
of networking hardware used in telecommunications networks that
allows data to flow from one discrete network to another. In another words, it
allows dissimilar networks to communicate. Gateways are distinct
from routers or switches in that they communicate using a
more than one protocol to connect a bunch of networks and can operate at any of
the seven layers of the OSI model. A network gateway provides interoperability between
networks and contains devices, such as protocol translators, impedance
matchers, rate converters, fault isolators,
or signal translators.
Modem
vs Router
A modem helps to
connect to the internet. It is associated with the ISP (Internet Service
Provider) and to a computer. Whereas a router connected with the modem helps to
share the internet with different other associated devices. Router has an
advantage of having an in-built security system to prevent it from hackers.
Bridge
vs Router
Router
is a device that connect multiple networks (two LANs or WANs or a LAN and
its ISP’s network) and forward data packets
destined either for its own networks or other networks. Bridge connects
a local area network (LAN) to another Local Area Network (LAN) that uses
the same protocols. Router operates in network layer
of OSI model and transmits data in the form of packets whereas bridge operates
in data
link layer of OSI model and transmits data in the form of frames.
Bridge has only two ports (single input and single out port) and reads the MAC
address of a device whereas router has more ports compare to a bridge and reads
the IP address of a device.
Switch vs Bridge
A bridge can connect
two similar networks together, whereas a switch can connect more network
segments as compared to the bridge.
Bridge analyzes and forwards one frame at a time whereas switch can
handle multiple frames at a time. Bridges have lesser number of ports as
compared to switch and are software based, while switches are hardware based
because they use ASIC (Application Specific Integrated Circuit) chips that help
to make filtering decisions.
Repeater
vs Amplifier
Amplifier and Repeater
are two types of electronic circuits used in communication. Some important
difference between Repeater and Amplifier are: (i) Repeater takes high input
power and provides low output power, whereas Amplifier takes low input power
and provides high output power. (ii) Repeater is generally used in static
(stationary) environment whereas Amplifier is generally used in Mobile and
Remote area network. (iii) Repeater regenerates the signal so that the noise
can be reduced or eliminated whereas Amplifier increases the amplitude of the
signal with the noise. (iv) Repeater
works on the physical layer of OSI model whereas generally Amplifier is used in
wireless communication. However, both are electronic devices, having 2 ports.
Li-Fi
vs Wi-Fi
Li-Fi (Light
Fidelity) is wireless communication technology, which utilizes
light to transmit data between devices. The term was first introduced by Harald
Haas in 2011. In technical terms, Li-Fi is a light communication system
that is capable of transmitting data at high speeds over the visible
light, ultraviolet, and infrared spectrum. However, Wi-fi is a
family of wireless networking technologies, based on the IEEE 802.11 family
of standards, which are commonly used for local area networking of devices
and Internet access. Wi‑Fi is a trademark of the
non-profit Wi-Fi Alliance. In contrast to Li-Fi, it uses Radio waves to
transmit data between devices.
SELF CHECK EXERCISES
1. Li-Fi
stands for __.
A. Light Fidelity
B. Low Fidelity
C. Large Fidelity
D. Loss Fidelity
2. In
data transfer process, which of the following is used for strengthening the
signals?
A. Hubs
B. Repeater
C. Switching Packets
D. Firewalls
3. Hubs
are networking device having __.
A. One port
B. Two ports
C. Multiple ports
D. None of the above
4. Select
the correct options about Amplifier
a) Amplifier takes low input power and provides high output power.
c) Amplifier increases the amplitude of the signal with the noise
d) Amplifier is used in wireless communication.
a) Amplifier takes low input power and provides high output power.
c) Amplifier increases the amplitude of the signal with the noise
d) Amplifier is used in wireless communication.
A.
a,
b, and d are correct
B.
a,
c and d are correct
C.
a
and d are correct
D.
b
and d are correct
5. Which
of the following technologies use electronic waves at radio frequency for data
transmission?
A. Li-Fi
B. Wi-Fi
C. Optical cables
D. Twisted Pairs
6. The device that is required to translate
digital signals into analogue form and back again is called a __.
A. Modem
B. Router
C. Connector
D. Switch
7. LANs (Local Area Networks) can be connected by
device called:
A. Bridges
B. Routers
C. Modems
D. Ethernet Cards
8. Which
of the following is not a switching system?
A. Packet
B. Circuit
C. Router
D. Message
9. A
router ___.
A. Forward data packets between telecommunication
networks
B. Receives
a signal and retransmits it at a higher level
C. Helps
in interfacing with another network
D. Essentially
translates protocols
10. The Network layer
concerns with __.
A. Frames
B. Bits
C. Packets
D. None of the above
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Thank u sir
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