Network & Communication Devices - Explained

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

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: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.


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. 
      b)      Amplifier is an electronic device having 4 ports
      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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