What is modem | Types of modem | How does the Modem work?

You must have heard the name of Modem before this, But do you know what is Modem, and How does the Modem work? By the way, you can connect your computer to the Internet only through a modem, through the existing telephone line.

Similar to computer Network Interface Card (NICs), modems are used to integrate with the computer motherboard. Contrast is available in a separate section to be installed in a PCI slot you can find on the motherboard.

Although a modem is not required in LANs, they are required in other Internet connections such as dial-up and DSL. Several types of modems differ from each other in speed and rate of transmission.

Standard PC modem or dial-up modem (56KB data transmission speed), cellular modem (which is used in a laptop and allows to connect at the same time), cable modem faster than standard modem) And DSL modems are also very popular.

so today I think you should tell me what is modem. you don’t need to search anywhere else. So let’s start without delay.

what is modem
what is modem

What is Modem

The full form of modem is “modulator/demodulator”. It is a hardware component that allows computers or other devices to be connected to computers or other devices over the Internet.

It converts or “modulates” the analog signal from the phone or cable into a digital signal that can be easily recognized by a computer. Similarly, it converts digital data into analog signals on computers or other devices.

Who found the Askir modem? In 1962, the first commercial modem was made and sold by AT&T with the Bell 103. Previous modems used to be “dial-up”, meaning they had to dial a telephone number to connect to the ISP.

This modem operates in standard analog telephone lines and also uses the same frequency as telephone calls, limiting its data transfer rate to a maximum of 56 kbps.

Dial-up modems also require total bandwidth from local telephone lines, which means voice calls can interfere with your Internet connection.

At the same time, modern modems are usually DSL and cable modems, also known as “broadband” devices. DSL models operate over the standard telephone line, but they use a wider frequency range.

They allow a higher data transfer rate if we compare it with a dial-up modem and it does not interfere with phone calls.

How does the Modem work?

As we have just learned that the full form of Modem is Modulator – Demodulator. Modems are also used because it transfers data from one computer network to another computer network.

In this, the transfer of data is done through the lines of the telephone. By the way, computer networks work in digital mode, while analog signal technology is used to send messages across phone lines.

The modulator converts the information in analog mode to end-to-end transmission from digital mode and the demodulator converts the same information about the same information from analog mode to end-to-end transmission.

Digitization is a process in which analog signals from computer networks are converted into digital signals in other computer networks.

When analog facilities are used, for data communication between two digital devices, they are called data terminal equipment (DTE), and modems are used at both ends. In such situations, the DTE can be a terminal or even a computer.

The modem presented at the end of the transmission, produced by DTE, converts it to an analog signal, as it is sufficient to modify the carrier. At the same time, the modem located on the receiving end transmits the display to the carrier and then the display digital signal arm ends up on the DTE.

The transmission media between two modems may be in the form of special circuits or telephone circuits. If telephone circuits are used, the modem is connected to local telephone exchanges.

Types of Modem

  • Directional capacity: half-duplex modem and full-duplex modem.
  • Connection to the line: 2-wire modem and 4-wire modem.
  • Transmission mode: asynchronous modem and synchronous modem.

Also Read:-

Half-Duplex modem and Full-Duplex modem:-


  • A half-duplex modem permits data for transmission in only one direction at a time
  • If the carrier is detected via a modem en route, it signals DTE to the incoming carrier via a control signal in the digital interface itself.
  • Until they get that indication, the modem does not allow DTE to transmit data.


  • In this duplex, the data flows on both sides in the same line.
  • Therefore in this duplex, there are two transmission carriers in the line, one outgoing and the other incoming.
2-wire modem and 4-wire modem:-

In the transmission medium, these modems have a line interface 2-wire connection or a 4-wire connection.

2-wire modem:-

  • A 2-key modem uses the same pair of cables for carrier in and out.
  • A leased 2-wire connection is often cheaper than a 4-car connection because they extend from just one pair to the premium of cable subscribers.
  • Connection data made through telephone exchange is also a 2-key connection.
  • In this 2-key modem, the transmission of half duplex mode which uses the same frequencies in two operators that enter and exit can be easily implemented here.
  • But for full-duplex operation mode, it is important that there are two transmission channels, one for distribution and one for receipt.
  • This multiplexing frequency division is achieved by both different carrier frequencies. This operator is stored in speaking channel bandwidth.
4-wire modem:-
  • In a 4-wire connection, one pair of cables is used in the outbound operators, and the other pair is used in the incoming carrier.
  • Full and half-duplex data transmission is possible in this 4-wire connection.
  • For example, the physical transmission route is different for each direction, so the same carrier frequency is used in both directions.
Asynchronous modem and Synchronous modem:-

Asynchronous modem:-

  • With the help of an asynchronous model for starting and stopping the bits, you can easily handle the data bytes.
  • Do not time signal or separate time between modem and DTE.
  • In this case, the internal timing pulses are repeatedly synchronized with the front edge of the credits.

Synchronous modem:-

  • The synchronous model can easily control the flow of data bits which are durable but they require a clock signal.
  • In this, the data bits are always synchronized with the clock signal.
  • It has a separate clock for the data bits which is transmitted and accepted.
  • Data For synchronous transmission of data, DTE is given as the internal clock and supplied in the modem.

Use of Modem

Basic modulation techniques used by modems to convert digital data into analog signals:-

  • Amplitude shift keying (ASK)
  • Frequency shift keying (FSK)
  • Phase shift keying (PSK)
  • Differential PSK (DPSK)

These techniques are also called continuous binary wave (CW) modulation.

Modems are always used in doubles. Any system, whether it is simplex, half-duplex or full-duplex, requires a modem to transmit and receive the tip

Hence we can say that a modem acts as an electronic bridge of action in two worlds – the first world which is a pure digital signal and the second world which is analog.

Function of modem

Modems are used to connect users to the Internet and send faxes. But if this problem is gone now, modems are now used in many applications in many businesses.

Many specialized applications include Data Transfer, Long Distance Management, Broadband Reserve, Sale of Points, Machine to Engine, and many more.

By the way, most of the solutions are located in the backend, so they are hidden from the users, but they work only with the backend and make our life easier every day.

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