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What are Modem and how many types are there?


What are Modem and how many types are there?

Do you know who has invented the modem and how it works? For more information about modem, please read this article.

Modem’s name you must have heard first. But do you know exactly what is Modem, how does it work? By the way, through a modem, you can connect your computer to 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 of which can be installed in PCI slots, which you can find in the motherboard.

By the way, a modem is not needed in the LAN, but they are needed in other Internet connections such as dial-up and DSL. There are many types of modems that differ from one another in Speed and Transmission rate. Standard PC modem or dial-up modems (56Kb data transmission speed), Cellular modem (which are used in laptops and enables it to be connected at the same time), cable modem (which is 500 times faster than the standard modem) and DSL Modems are also very popular. So today I thought why people should not be told what you are talking about in Modem so that you do not need to find people anywhere in this subject. Then let’s begin without delay.

What is the modem?

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

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

The modern modems are typically DSL and cable modems, which are also called “broadband” devices. DSL modems operate on standard telephone lines, but they use a wider frequency range. These allow high data transfer rates if we compare it with dial-up modems and also do not interfere with these phone calls as well.

What is the Router and how it works?

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

NOTE: Since a modem converts analog signals into digital and vice versa, therefore they need ADC or DAC. Modems are not necessarily in fiber optic connections because they transmit signals digitally from beginning to end.

How does modem work?

As we know Modem’s full form is the Modulator-Demodulator. Modems are used to transfer data from a computer network to another computer network. This is done through data transfer telephone lines. By the way, the computer network works in digital mode, the same is used to send analog technology across the phone lines.

The modulator converts information from digital mode to transmitting end in analog mode and the same demodulator converts the same information from analog mode to the digital mode in the receiving end. Digitizing is called the process in which the analog signals of a computer network are converted into digital signals in any other computer network.

When an analog facility is used, for data communication, between two digital devices, then they are called Data Terminal Equipment (DTE), the modems are used in both ends. In this case, DTE can be either a terminal or a computer.

The modem that is present in the transmitting end, converts the digital signal which is generated by DTE into an analog signal, for that it simply modulates the carrier. The modem, which is in the receiving end, demodulates the carrier and then later that demodulated digital signal is handed over over DTE.

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

Modem definition

Initially, Data Terminal Equipment or DTE (also known as a computer) sends a Ready To Send or RTS signal, Data Communication Equipment or DCE (also called a 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 the signal is sent in a series of channels until one communication channel is established. This process is called handshaking.

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

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

Nevertheless, in the minds of the majority, this question will be essentially how the data is transferred from one computer to the other. That’s because the phones are analog and the computers are digital. In simple words, a telephone signal is constantly changing. To understand this, think about a sine wave that is produced by e Oscilloscope. Although this sign seems constant, in reality it is constantly changing, from positive to negative and then vice versa, in the series of smooth curves.

On the other hand, computers can understand only the information that they are presented in terms of the string of binary digits. So the main idea here is to map the digital output to the analog signal.

Modem Information

Regardless of its technicalities, it done by superimposing the different frequencies in the analog signal (which we later call the Carrier Wave). Different frequencies represent binary digits of different groups in this process, which is called modulation. When it transmit and decode in the receiving end, it is called demodulation. Actually, two types of communication are achieved through a single device in which both modulation and demodulation come, so this device is called Modem.

From this, one thing is obvious that the higher the frequency in which the superficial superficiation is done in the carrier wave, the data transmit even faster. By understanding it in another way, more data is transmit when more frequencies are needed.

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

Types of Modem

Well, there are many types of Modems and those which are categorized in many ways. Let’s now know about them.

Let us know Categorization based on these following basic modem features:
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 in the incoming carrier in DTE, which is done through a control signal in its own digital interface.

3. As long as they do not get the indication, the modem DTE does not allow the data to transmit.

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

2. Therefore, there are two carriers in the line, one outgoing and the second incoming.

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

4-wire Modem
1. In a 4-wire connection, a pair of wires is used in the outgoing carrier, the second pair is used in the incoming carrier.

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

3. As for the path of the physical transmission 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 cheap compared to a 4-wire connection because only one pair of wires is extended to the subscriber’s premises.

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

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

5. But for full duplex mode of operation, it is necessary to have two transmission channels, for a transmit direction, for the second received direction.

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

Asynchronous and Synchronous Modems

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

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

3. In this, internal timing pulses are repeatedly synchronized with Start Pulse’s leading edge.

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

2. In this data, bits are always synchronized by the clock signal.

3. There are separate clocks for data bits that transmit and receive.

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

Modem Uses

Basic modulation techniques 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. Whether any system, whether it is simplex, half duplex or full duplex, they need a modem, that too in transmitting and receiving end.

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

Modem functions

Modems were originally used to connect with the Internet and send the fax to users. But if the thing is done now, modems are now being used in many applications in many applications. There are some special applications such as data transfers, remote management, broadband backup, the point of sale, machine to machine and many more. By the way, most of the solutions are in the backend, so users are hidden from it but they work from backend and make our lives easier every day. 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 which most consumers use every day. Whenever you pay by using a credit card or debit card anywhere in a shop, then they use a modem (dial-up or broadband) and behind the data transfer.

Examples of Point of Sale
In the Credit Card Payment Terminal restaurant, in movie theaters, or in retail stores,
In train stations, in Ticketing machines, bus stations, and airports, 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 remotely controlled only with the help of modem and the user does not need to go to the actual location. This saves both time and money, as well as protects against accidental issues, or issues that require quick actions and require instant configuration changes.

Examples of Remote Management, Maintenance or Logistics1. On Stoplight Timing Control – This can be done from the headquarters to regulate the traffic flow, which has the ability to change the signal timing.

2. Changing Roadside Digital Signs – This is the ability to change messages from the headquarters.

3. Grocery Store Freezer and Cooler Call Center – The ability to monitor temperature, along with status, also get the automatic alert.

4. Safe company – The ability to check the temperature.

5. The Irrigation system of Golf Course – Control the use of Sprinklers’ timings and simultaneously monitor their consumption.

6. Vending machine inventory and status – What are some things you need to know before reaching the site.

7. Maintenance of Gas / Petrol station – When a credit card operated pump is down, then an alert should automatically relay. In a central point, it is also in 24 hours a day.

Data Transfers

There is a headquarter location in large companies where all the data is centrally located. This means that all other locations send data daily to that HQ in a daily basis. Dial-up modem solutions are very ideal because they can be programmed every time the data can be sent with secure connections. This reduces the failure of data transfer, along with these are also very cheaper.

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

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

Machine to Machine (M2M) Communication
Machine solutions are typically a communication link that connects two machines (computers, electronic devices) with each other and which are capable of transferring data when they need them. It does not require any human interference.

Machine communication example from machine
Medical devices that transfer test results to Doctor’s computer which is in their office.

What are the other applications
There are many different applications where the modems are use. So let’s know about them.

1. In the home security monitoring – a modem use in it to send a voice message to the telephone/mobile when the alarm stops.

2. On the circuits in cell phone tower maintenance

3. In the gasoline vapor containment system

4. In Property listings

5. In Cinema screening approval – A serial port modem use. To authorize a coded key to run which movie to be run on screen.


I hope you have my favorite article in this article . It always my endeavor that readers should be given full information about the modem full form so that they do not need to find any other sites or internet in the context of that article. This will also save their time and will get all the information in one place. If you have any doubts about this article in your mind or you want some improvement in it then you can write down comments for it.

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