Hardware devices that are used to connect computers, printers, fax machines and other electronic devices to a network are called network devices.
These devices transfer the data in a fast, secure and correct way over same or different networks.
Some devices are installed on the device, like NIC card or RJ45 connector, whereas some devices are the part of the network, like router, switch, etc.
NIC&RJ45
Modems
Modem is abbreviation for Modulator – Demodulator.
Modems are used for data transfer from one computer network to another computer network through telephone lines or cable lines.
The main function of the modem is to convert digital signal.
The modulator converts digital data into analog data when the data is being sent by the computer.
The demodulator converts analog data signals into digital data when it is being received by the computer into analog and vice versa.
Modems can be of several types and they can be categorized in a number of ways like,
Direction in which it can transmit data (Simple, Half Duplex, Full Duplex)
Type of connection to the transmission line (2 wire mode, 4 wire modem)
Transmission mode (asynchronous, synchronous)
Types of Modem- Depending on direction of data transmission, modem can be of these types
Simplex − A simplex modem can transfer data in only one direction, from digital device to network (modulator) or network to digital device (demodulator).
Half duplex − A half-duplex modem has the capacity to transfer data in both the directions but only one at a time.
Full duplex − A full duplex modem can transmit data in both the directions simultaneously.
Types of Modem- Depending on the Transmission mode
Asynchronous Modem- Asynchronous modems can handle data bytes with start and stop bits.There is no separate timing signal or clock between the modem and the DTE.
Synchronous Modem- Synchronous modems can handle a continuous stream of data bits but requires a clock signal. The data bits are always synchronized to the clock signal.There are separate clocks for the data bits being transmitted and received.
Types of Modem- Depending on the Type of connection to the transmission line
2-wire modem
In 2-wire modems use the same pair of wires for outgoing and incoming carriers.
4-wire modem
In a 4-wire connection, one pair of wires is used for the outgoing carrier and the other pair is used for incoming carrier.
Routers
A router is a network layer hardware device that forwards data packets between computer networks.
Routers perform the traffic directing functions on the Internet.
Data sent through the internet, such as a web page or email, is in the form of data packets.
A packet is typically forwarded from one router to another router through the networks that constitute an internetwork (e.g. the Internet) until it reaches its destination node.
Switches
Switch is a network device that connects other devices to Ethernet networks through twisted pair cables.
It uses packet switching technique to receive, store and forward data packets on the network.
The switch maintains a list of network addresses of all the devices connected to it.
On receiving a packet, it checks the destination address and transmits the packet to the correct port.
The data is transmitted in full duplex mode
Gateways
Gateway is a network device used to connect two or more dissimilar networks.
The gateways are used to connect two networks that do not communicate with the same network protocol, so it is necessary to translate these protocols between both networks.
A gateway usually is a computer with multiple NICs connected to different networks.
A gateway can also be configured completely using software.
Gateway uses packet switching technique to transmit data from one network to another.
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