What is modem and how many types are there?

You must have heard Modem’s name before. But do you know in the right form what is Modem , how does it work? By the way, through a modem you can connect your computer with the available Internet connection through the existing telephone line. Like NIC, Modem is used to integrate with the computer motherboard . Rather it is available as a separate part which can be installed in PCI slots which you can find in the motherboard.

What is modem
What is modem

By the way, a modem is not required much in LAN, but they are needed in other internet connections like dial-up and DSL. There are many types of modems that differ from each other in Speed ​​and Transmission rate. Standard PC modem or dial-up modems have (56Kb data transmission speed), Cellular modem (which are used on the laptop and enable it to connect at the same time), cable modem (which is 500 times is faster than standard modem) and DSL Modems are also very popular. So today I thought that why should you people explain what Modem is in Hindi, so that you people do not need to find somewhere else about it. Then let’s start without delay.

What is Modem?

The full form of a Modem is “ Modulator / Demodulator .” It is a hardware component that allows a computer or other device, such as a router or switch, to connect to the Internet. It converts or “modulates” an analog signal from a telephone or cable wire to a digital signal that a computer can easily recognize. Similarly, it converts outgoing digital data into analog signal in a computer or other device.

Who invented the asphyxia modem? In 1962, the first commercial modem was manufactured and sold by AT&T as the Bell 103. Earlier modems used to be “dial-up,” meaning they have to dial a phone number to be connected with ISP. These modems operate in standard analog phone lines and also use the same frequencies as telephone calls, which limits their data transfer rate to a maximum of 56 Kbps. Dial-up modems also require full bandwidth of the local telephone line , which means that voice calls can interrupt your internet connection.

Valid Modern Modems Typically DSL and cable modems, are among the ” Broadband ” Devices are also called. DSL modems operate over standard telephone lines, but use a wider frequency range. They allow for higher data transfer rates if we compare it with dial-up modems and also they do not interfere with phone calls.

Cable modems send and receive data in standard cable television lines, which are typically coaxial cables. Most modern cable modems support DOCSIS ( Data Over Cable Service Interface Specification ), which provides an efficient way to easily transmit TV, cable Internet, and digital phone signals into the same cable line.

NOTE: Since a modem converts analog signals into digital and vice versa, they require ADC or DAC . Modems are not required in fiber optic connections as signals are transmitted digitally from start to finish.

How does modem work?

As we know that Modem has full form Modulator – Demodulator. Modems are used to transfer data from one computer network to another computer network. In this, data transfer is done by telephone lines. Although the computer network works in digital mode, the analog technology is used to send messages across the phone lines.

The modulator converts the information from digital mode to analog mode at the transmitting end and the same demodulator converts the same information from analog mode to digital mode at the receiving end. Digitizing is the process in which analog signals from one computer network are converted into digital signals from another computer network.

When an analog facility is used between two digital devices for data communication then they are called Data Terminal Equipment (DTE), modems are used at both end. In such a situation, DTE can be either a terminal or a computer.

The modem that is present at the transmitting end converts the digital signal generated by DTE into Analog Signal , for which it modulates the bus carrier. The modem that is present at the receiving end demodulates the carrier and then later that demodulated digital signal is hand over in DTE.

The transmission medium between the two modems can be either a dedicated circuit or a switched telephone circuit. If a switched telephone circuit is used, the modems are connected to local telephone exchanges.

Modem definition

Initially, Data Terminal Equipment or DTE (also called computer) sends a Ready To Send or RTS signal, Data Communication Equipment or DCE (also called modem). It is also sometimes called a wakeup call and as a result it sends a Data Carrier Detect or DCD signal receiving modem. Then a series of signals are sent within these two until a communication channel is established. This process is called handshaking.

After this, the second modem now sends a Data Set Ready or DSR signal to the computer and then it waits for Data Terminal Ready or DTR reply. When this happens, the first modem sends a Clear To Send or CTS signal to the computer and this starts the whole process and the data is easily transmitted.

To complete this process, these signals are sent to plug-in different pins and therefore handbooks of all modems and printers carry a pin diagram in troubleshooting in this section. They were also standardized when the other industry leaders agreed to that standard for peripheral equipment of all range. Therefore RS 232 cable is considered standard all over the world.

Yet in the minds of many people, this question will surely be how the data is transferred from one computer to another. This is because phone lines are analogous while computers are digital. In simple words, a telephone signal is constantly changing. To understand this, think of a sine wave that has been produced by e Oscilloscope. This signal may seem constant, but in reality it is constantly changing from positive to negative and then its reverse in a series of smooth curves.

On the other hand, computers can understand only the information that can be presented according to the string of binary digits. So the main idea here was how to map digital output to analog signal.

This is done without taking into account its technicalities by superimposing different frequencies into the analog signal (which we will later also call Carrier Wave). Different frequencies represent binary digits of different groups in this process, which is called modulation. At the same time when it is transmit and decoded at the receiving end then it is called Demodulation. Basically two types of communication are achieved by a single device in which both modulation and demodulation occur, hence this device is called Modem.

One thing is clear from this that the more the frequencies can be superimposed in the carrier wave, the faster the data can also be transmitted. Understand this another way, then more data is transmitted when more frequencies are required.

Remember one thing that only a limited amount of frequencies can be sent at a time and it is called Key Bandwidth. Now, the data comes very large such as pictures, sound and video sequences which are transmitted on a regular basis through the Internet.

Types of Modem

By the way, there are many types of Modems and which are categorized in many ways. Let us now know about him only.

Let’s know categorization based on these following basic modem features:
1. Directional capacity : half duplex modem and full duplex modem.
2. Connection to the line : 2-wire modem and 4-wire modem.
3. Transmission mode : asynchronous modem and synchronous modem.

Half Duplex and Full Duplex Modems

Half duplex

1. A half duplex modem permits transmission in only one direction at the same time.

2. If a carrier is detected by the modem in the line, then it gives an indication to the incoming carrier in the DTE which is done via a control signal in its own digital interface.

3. The modem does not give permission to DTE to transmit data until they get that indication.

Full Duplex

1. A full duplex modem allows simultaneous transmission in both directions.

2. Therefore it has two carriers in line, one outgoing and the other incoming.

2-Wire and 4-wire Modems

The line interface of these modems can be either a 2-wire connection or a 4-wire connection, in transmission medium.

4-wire Modem

1. In a 4-wire connection, one pair of wires is used in the outgoing carrier while the other pair is used in the incoming carrier.

2. Data transmission of full duplex and half duplex modes is possible in these 4-wire connection.

3. As the physical transmission path is different for each direction, the same carrier frequency is used in both directions.

2-wire Modem

1. 2-wire modems use the same pair of wires for outgoing and incoming carriers.

2. A leased 2-wire connection is often cheaper than a 4-wire connection as only one pair of wires are extended to the subscriber’s premises.

3. The data connection that is established through Telephone Exchange is also a 2-wire connection.

4. In these 2-wire modems, the transmission of half duplex mode which uses the same frequency in both incoming and outgoing carriers, can be easily implemented here.

5. But for full duplex mode of operation, it is necessary to have two transmission channels, one for the transmit direction and the other for the receive direction.

6. This is achieved by frequency division multiplexing of both different carrier frequencies. These carriers are kept within the speech channel’s bandwidth.

Asynchronous and Synchronous Modems

Asynchronous Modem

1. Asynchronous modems can handle data bytes easily with the help of start and stop bits .

2. There is no separate timing signal or clock between modem and DTE.

3. In this the internal timing pulses are synchronized repeatedly with the leading edge of the Start Pulse.

Synchronous Modem

1. Synchronous modems can easily control a continuous stream of data bits but they require a clock signal.

2. The data bits in it are always synchronized with the clock signal.

3. It consists of separate clocks for data bits which are transmit and receive.

4. For synchronous transmission of data bits, DTE is given the same as its internal clock and supply in the modem.

Modem usage

Basic modulation techniques that are used by a modem to convert digital data to analog signals:

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

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

1. Modems are always used in pairs. Any system, whether it is simplex, half duplex or full duplex, definitely needs a modem in the transmitting and receiving end.

2. Therefore we can say that a modem acts like an electronic bridge between two worlds – the first world which is purely digital signals and the second one the established analog world.

Modem functions

Modems were originally used to connect users with the internet and to send fax. But if we talk now, then modems are now being used in many applications in many businesses. There are some special applications like data transfers, remote management, broadband backup , point of sale, machine to machine and many more. By the way, most solutions are located in backend, so they are hidden from users, but they work from backend itself and make our life easier everyday. Below I have used some such examples.

Point of Sale (PoS)

The full form of PoS is Point of Sale. This is a very heavily used application that most consumers use every day. Whenever you pay using a credit card or debit card in a shop somewhere, then they use only a modem (dial-up or broadband) and behind the data transfer.

Point of Sale Examples
Credit Card Payment Terminal in restaurants, movie theaters, or retail stores,
in ticket stations, bus stations, and airports in train stations, pre-pay gas pumps, ATM cash machines

Remote Management, Maintenance, & Logistics

Modems can be installed in remote locations in off-site locations, tight enclosures, or within sensitive locations. Some applications can be controlled remotely only with the help of modem and there is no need for the user to go to the actual location. This saves both time and money, as well as prevents accidents or issues that require quick actions and instant configuration changes if needed.

Examples of Remote Management, Maintenance or Logistics
1. On Stoplight Timing Control – This can be done from the headquarters to regulate traffic flow, which has the ability to change the signal timing.

2. Changing Roadside Digital Signs – Ability to change messages from headquarters.

3. Grocery Store Freezer and Cooler Call Center – Ability to monitor temperature and status as well, besides automatically receiving alert.

4. Safe company – ability to check temperature.

5. Irrigation system of Golf Course – Control the timings of usage of sprinklers and simultaneously monitor their consumption.

6. Vending machine inventory and status – Know what is needed before reaching the site.

7. Maintenance of Gas / Petrol station – When a credit card is operated pump down, then an alert is automatically relayed to a central point for 24 hours a day.

Data Transfers

Most big companies have a headquarter location where all the data is centrally located. This means that all other places send data on a daily basis to that HQ. Dial-up modem solutions are very ideal because they can be programmed to send data with secure connections every day. This reduces the failure of data transfer significantly, along with it they are also very cheap.

Examples of data transfers
1. Synchronization of data from other branches in a headquarter location

2. Daily Sales information should be sent automatically from all branches to the headquarter location.

Machine to Machine (M2M) Communication

Machine to Machine solutions typically have a communications link that connects two machines (computers, electronic devices) with each other and is capable of transferring data when they are needed. There is no need for any human intervention in this.

medical devices of machine-to-machine communication that transfer test results to the doctor’s computer which is located in their office.

What are the other applications

There are many different applications where modems are used. So let’s know about them.

1. In home security monitoring – in this a modem is used to send a voice message to a telephone / mobile when the alarm goes off.

2. Cell phone tower maintenance in circuits

3. Gasoline vapor containment system

4. In Property listings

5. In cinema screening approval – a serial port modem is used to send a coded key to authorize which film to run on the screen.


I hope you have liked this article about what is modem . It has always been my endeavor to provide complete information about the modem full form to the readers, so that there is no need to search them in the context of that article in any other sites or Internet. This will also save their time and they will also get all the information in one place. If you have any doubts about this article or you want that there should be some improvement in it, then for this you can write down comments. If you liked this post in Hindi like modem or got to learn something, then please share this post on social networks like Facebook , Google+ and Twitter etc.

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