What is Modem? Features, Function, Types, Uses & More

What is Modem

What is Modem?

The term ‘Modem’ is actually a short for Modulator and Demodulator. It refers to a device that modulates or changes signals for encoding digital information before transmission. At the same time, the device demodulates the signals for decoding the information transmitted.


  • The modem allows the computer to send data by using a physical telephone line. It is used broadly for telecommunications.
  • A modem is used in personal computers to send emails and also in other devices to send or receive fax messages and even for downloading things from the internet and lots of other purposes.
  • A modem can be considered as an input device as well as an output device because it receives or downloads or input data and also sends or uploads or output data both.

Understanding Modem

What is Modem

A modem is a device that converts digital data into signals. It is then easier to transmit the data over a medium which can be either a phone line, a cable, or via a satellite connection.

The most common and popular mode of accessing the internet by using a modem is through a dedicated telephone line which is usually analog in nature.

In these cases the modem converts the computer data between digital and analog formats in real time.

This helps in establishing a two-way network communication.

Technically speaking, a modem refers to that network device which can modulate as well as demodulate analog signals, which are also called the sine waves, and used for encoding and decoding the digital data for processing.

The modems are designed to accomplish this task at the same time.

Therefore, a modem is used most commonly for receiving and sending digital information between two computers that are typically transmitted over the telephone lines.

Latest dial-up standard such as V.92 is used for that matter. Today, broadband modems are used to access the internet at high speed.

In simple terms, a modem is the short term that stands for modulator and demodulator and refers to the device that is used to transform one type of signal to another in the computers.

As you may know already, in a computer the digital data is always represented with binary code which is actually a sequence of 0s and 1s.

Here, 0 signifies “off” and 1 signifies “on.”

With the help of a binary code anything can be represented such as:

  • Words
  • Pictures
  • Symbols
  • Videos and
  • Sound.

Each 0 or 1 in the binary code in a computer is called a bit or binary digit and a computer typically uses the ASCII or American Standard Code for Information Interchange which is also the standard that is used by the modem for coding.

When a computer creates a digital code it changes that signal to another form in order to carry it to another computer.

However, in order to let the second computer read it, this signal is again changed back into digital code.

Therefore, ideally, the mode works in two modes as follows:

  • As a modulator, the device that converts digital data from one computer into analog signals so that it can travel through the phone lines to another computer easily and
  • As a demodulator, the device that receives the analog signals and then again converts back into digital signals which can be read easily by the second computer that received it.


Taking a look at the brief history of the modems, the first modem was called the Dataphone. It was developed by AT&T and was released in 1960.

This specific type of modem was more commonly used by the home users when the 80-103A modem was developed by Dennis Hayes and Dale Heatherington and released in 1977.

The commercial modems were used for the first time by larger organizations such as:

  • News services
  • Large businesses and
  • The US Department of Defense.

Over time, the modems became more familiar to the general consumers and more devices were built in the late 1970s through the 1980s to support the early internet infrastructure.

Later on, when the World Wide Web ‘exploded’ in the mid and late 1990s, the dial-up modems were designed.

These modems became the primary medium to access the internet and were used in several homes all over the world.

Typically, in the early 2000s, the dial up modems were used more commonly in the computers to connect to the internet.

Later on, these types of modems lost their prominence when the broadband internet started and was used more widely.

Today, the dial-up modems are not used in computers anymore, now that the broadband internet is more widely available.

This is now the most popular means to connect between computer systems and the internet.


From the dial-up modems to the Wi-Fi modems, these devices have evolved dramatically over the years.

Dial-up modems:

The dial-up modems used the dial-up networks to convert analog data used in the telephone lines and digital data used by the computers as required.

In most cases the earlier dial-up modems are connected externally to the computer though there are a few specific computer models that came with an in-built dial-up modem.

Since the computers use digital signals and the phone lines through which the modems establish a connection use analog signals, the modems usually make a squealing noise while establishing a connection, a process called handshaking.

This sound is actually made when digital information is transmitted over an analog line.

When the connection is completed, the modem goes silent.

Broadband modems:

With development in technology, the dial-up modems made way to the broadband modems.

A broadband modem typically uses DSL or cable internet access. They also used advanced signaling techniques.

These features allow these devices to attain dramatically high network speeds in comparison to the older dial-up modem models.

It is for this reason that the broadband modems are typically referred to as high speed modems.

Cellular modem is a type of digital modem that allows connecting a mobile device to a cell phone network to access the internet.

The external broadband modems are typically plugged into a broadband router or any other gateway device at home on one end and to an external internet interface on the other such as a cable line.

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The gateway or the router directs the signals to the desired devices as needed.

However, there are a few specific types of broadband routers that come with a modem integrated as one single hardware unit in them.

If not, the broadband internet service providers supply a proper hardware modem to their customers either free or for a monthly fee.

Wi-Fi modems:

Then there are the Wi-Fi modems that are specifically designed to broadcast a wireless signal which is also referred to as a Wi-Fi network.

It also offers a conventional wired connection.

Most of the modern modems available today come with Wi-Fi support built in.

However, you should not mix up a modem with a router that you usually have in your home.

These two are completely different devices though they share the similar functionality or serve the same purpose of accessing the internet.

As said earlier, a modem, traditionally, handles the connection of the computer to the internet.

On the other hand, the router helps in connecting multiple devices to the internet at the same time.

In addition to that, the router also allows the devices to communicate with each other without needing to access the internet.

Features of Modems

The modern modems come with several useful features and some of the most useful ones are:

  • High uploading rate that may range anywhere between 28.8 KB/s and 56 KB/s depending on the type
  • High communication rate
  • Higher upgradability via a software patch so that it can comply with any given universal standard
  • High speed data downstream transfer rate to transfer data digitally
  • High data upstream rate of about 33.6 KB/s
  • Dual Simultaneous Voice and Data or DSVD feature is some models that can carry both computer data and analog voices data
  • Ability to act as caller ID by detecting the callers originating telephone numbers and
  • Advanced voice mail features in some models which act as intelligent digital information systems and answering machines.

There are also a few other features and standards of modems that make these devices all the more useful. These are:

  • The auto-answer feature which allows the modems to answer the phone automatically after it rings for a set amount of time
  • The data/voice features which give the modems the ability to switch between a data and voice communication
  • The fax messaging feature in some modems that allow the device to send or receive fax messages with the help of the right software and
  • The V.90 standard which allows the modems to communicate between two devices at a very high speed.

There are several of these standards introduced but almost all 56 K modems normally use the V.90 standard.

Working Process

The modulator/demodulator, or a modem, allows the computer to send or receive data by using the telephone lines.

As said earlier, when signals are sent, the device converts them from digital data signals to analog audio signals, a process called modulating.

This analog audio signal is then transmitted over the dedicated telephone lines to another device where it is demodulated or converted back to digital signal.

According to the communication type, ideally, the modems are considered to be asynchronous devices.

This means that these devices transfer data in a discontinuous stream of tiny packets.

When these packets are received by the destination device, these are reassembled into a particular form which the computer can understand and use.

Therefore, the modems allow an asynchronous communication. In this type of communication, a single byte, which consists of 8 bits, is transferred in a single packet which is the same as one character.

Technically, every packet needs to contain a Start and Stop bit for the destination computer to receive the information in packets.

This means that every packet needs to be of 10 bits in order to be a complete packet.

For example, if you transmit a word ‘Hi,’ it will be equal to two bytes or of 16 bits and would consist of two packets of 10 bits each.

And, each of these 10-bit packets would consist of:

  • Start – 1 bit
  • Data – 8 bits and
  • Stop – 1 bit.

This makes a complete 10-bits packet.


The speed of the modem is typically measured in bits per second or kilobits per second.

Most of the modern modems can send or receive signals at a speed of 56 K or 56,000 bps.

This is considered to be the fastest rate of data transfer in today’s dial-up modems.

However, the data transfer speeds of the modems were not always high. In fact, it was annoyingly slow initially but over time with the development in technology the transfer speed of signals increased gradually, in the following order:

  • 110 baud
  • 300 baud
  • 1200 baud
  • 2400 baud
  • 4800 baud
  • 9600 baud
  • 14.4 K
  • 28.8 K and
  • 33.6 K to reach today’s level of 56 K.

Here baud is the unit of measure that is named after Emile Baudot.

However, there are a few specific factors that will determine the actual speed of the modems, even if it is rated 56 K.

The two major factors that will determine its speed are:

  • The quality of the phone line used to communicate over and
  • The number of collocations used.

These two have to be optimal if you want the modem to attain its highest speed while transferring signals to and from.

In addition to that, if one modem with a higher speed establishes a connection with another with lower speed, the device will use the slowest speed possible.

Importance of Modem in a Computer

A modem is quite important for a computer because it allows sharing data, information and files between different computers. This can be any type of data such as:

  • Messages
  • Images
  • Videos
  • Sound and others.

This is one single device that works both as a modulator and a demodulator, or in other words, converts digital signal into analog form and vice versa in order to facilitate the transfer.

Apart from that, a modem is also important due to some other good reasons as well such as:

  • It helps in sharing both hardware and software resources
  • It helps in requesting and loading several facilities offered by the internet
  • It helps in transferring high quality data between devices faster that helps businesses to communicate faster and offer better customer support in real time
  • It helps in rendering good quality graphics which helps a lot in creating gaming and multimedia graphics in 3D and in Java
  • It helps in creating Local Area Network or LAN in homes, healthcare centers and entertainment industry in an inexpensive way for faster communication and better service
  • It helps doctors, lawyers and other government officials to reach out to people in remote places to offer their services where they usually do not go to and
  • It helps the economy of a country to grow because most businesses today are done online and a deal can be closed quickly via the internet.
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A modem is also important for other reasons such as decreasing the time in data transfer because it has the ability to compress data while sending them.

This feature also reduces the chances of errors during the flow of signals because the data compression mechanism reduces the size of the signals considerably.

In some specific types of modems, there is also an error correction feature included.

In this technique, the device makes sure that all the data received is undamaged before splitting it into small units called Frames.

These frames are tagged along with the checksums before sending.

This special technique helps in checking the redundancy in the data presented in a computer.

The data is sent only when it matches with the checksums or else it is moved back.

The different speeds in which a modem sends the signals allow in controlling the flow of data.

This enables the slow signals to pause the faster signals by sending a ‘character’ in order to prevent any issues while receiving signals.

When such a character is sent by the slower signal and is received by the faster signals, the latter will pause until the slower modem catches up.

In short, a modem helps in modifying digital signals into precise analog signals and in line control while sending signals to other phone edges.

It also helps in securing the data transmission process when there are any specific issues such as line overloading and others.

Uses of Modem

A modem is typically used for different purposes in a computer.

A modem is widely used to translate the ASCII or American Standard Code for Information Interchange codes into another format and send it to another location.

It is then translated back into the ASCII code.

Today, the modems are used in different areas to communicate with other devices. Here are some of those areas with a brief description against each.

Point of Sale

Commonly referred to as PoS, modem plays a major role here, when consumers want to make a payment for their purchase through credit card, debit card, or via net banking.

The modem not only helps in sending the data but also helps in returning an approval for the desired transaction.

A few examples of PoS are:

  • ATM machine
  • Online shopping through net banking
  • Paying bills through credit card or debit card in hotels, cinemas and shopping malls and
  • In the ticketing machines in airports, bus and railway stations.

Remote Management, Logistics and Maintenance

Modems are also used extensively at off site locations in remote locations, sensitive locations or tight enclosures.

This saves from the hassles of visiting those places but still allows managing the applications without place limitations, which also saves time and money in travel.

Some of the examples of such locations are:

  • Gas and petrol station maintenance
  • Grocery store freezer
  • Cooler call center
  • Roadside digital signs
  • Vending machine status and inventory
  • Stoplight timing control and
  • Golf course irrigation system.

Out of Band Access, Server and Broadband Backup

Several large and small businesses use broadband connectivity to communicate with their employees.

In this case, the modems help in this communication with the need for a reliable backup during down speed of server or broadband connections.

This is more commonly referred to as ‘Out of Band Access.’

A few examples of it are:

  • Server backup
  • Backup for ADSL connections in car washes, DVD rental and others and
  • Backup for VPN or Virtual Private Network dial in connections.

Data Transfers from Franchise to Headquarter

Modems also help those large scale organizations that have their head office located somewhere else but needs all the data to be sent there by their franchises.

The modem provides a protective connection to ensure reliable transfer of data in such cases.

A few examples are:

  • Sending daily sales data to the headquarter and
  • Synchronizing the data received at the headquarter location from other branch offices.

Machine to Machine Communication

Modems also help in communicating between machine to machine by transferring data from one to another without needing the help of interaction of the users.

One of the most significant use cases of it is in the medical devices for transferring test reports of patients to the computer of the concerned doctor.

There are also a few other areas where a modem is extensively used and these are:

  • At homes for surveillance and security monitoring
  • In cinemas for screening approvals
  • For property listings
  • For maintenance of the cell phone towers and
  • In gasoline vapor containment systems.

Therefore, in short it can be said that modems are widely used in almost every place where a computer is used nowadays.

Types of Modem

There are mainly two types of modems available in the market namely the standard modems and the window modems.

Standard Modems:

The specific types of modems typically have generic device drivers in them that can be either internal or external ones where each of them has different functionalities and requirements.

For example, the internal modems usually do not require much physical structure and can be installed into a slot as long as it is compatible.

On the other hand, the external modems typically need a COM port in order to be connected to a computer that usually has a cable specifically known as the null-modem cable.

Window Modems:

These specific types of modems are more like a private plug and play device that needs a specific type of device driver that supports Windows operating framework in order to function in the right way.

However, apart from the broad categories of modems, these devices for carrying signals can be further divided into the following categories based on their respective designs and features:

  • Optical Modem – These modems use optical cables in place of any other types of metallic media. These modems convert the digital signals into a pulse of light. This is transferred through the optical fibers.
  • Digital Modem – These types of modems are designed to change digital data into digital signals by modulating the former into digital carrier signals before transmitting them through the digital transmission lines.
  • Acoustic Modem – This particular type of modem is designed to combine the telephone handset with a device and also comes with a microphone and a speaker. These specific types of modems are very useful for those salespersons who travel a lot. These devices help them to connect their device to the phone lines of the hotels.
  • Smart Modem – This type of modem comes with advanced features such as auto-dial, auto-redial, auto-answer and others. There is an onboard microprocessor as well in these particular types of modems which enhances the auto answering and auto dialing capabilities via the Hayes AT command set.
  • Short Haul Modem – These types of modems are usually found in homes connected to the computer. These modems can transfer data up to 20 miles or less and are usually used to connect the computers in an office or a building within this limit.
  • ADSL Modem – A short for Asymmetric Digital Subscriber Line, these modems also use the telephone lines to send and receive signals but are very fast as compared to traditional modems. These devices use synchronous and asynchronous data transmission methods for more accuracy and better timing of signals and correcting formulas respectively.
  • DSL Modem – A short for Digital Subscriber Line, these modems are also referred to as broadband modems that provide broadband services to use different types of internet connections. These modems are very comfortable to use to access high speed internet.
  • Router and Modem Combo – These particular types of modems come with a router installed in them. It allows connecting several different computers and devices in a single network without needing an additional router for the same.
  • Integrated Modem – These are those particular modems that are embedded into the computer. These are usually in the form of a PCI or USB card. However, these modems allow only one computer system to connect to the internet.
  • Fax Modem – Just as the name suggests, these specific types of modems allow the users to send or receive any text document over the telephone line and it also acts like a fax machine.
  • ISDN Modem – A short for Integrated Services Digital Network, these particular types of modems offer communication standards for digital transfer of video or voice data over optical fiber or wire.
  • Intelligent Modem – These are costly modems that come with specific features such as diagnostic error checking, internal ROM or Read Only Memory coding, and microprocessor chips. These features offer more refined communications protocols.
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Based on their design, the modems can also be of a few other different types such as:

  • Onboard modems that are built onto the motherboard of the computer and cannot be removed but disabled through the BIOS or Basic Input Output System setup or via a jumper
  • Internal modems that use a PCIe or Peripheral Component Interconnect Express slot in a new computer or an ISA or Industry Standard Architecture slot in an old computer to connect
  • External modems that are like a box connected to the computer through a USB or Universal Serial Bus port or a serial port and
  • Removable modems that are used in older models of laptop computers that use a PCMCIA or Personal Computer Memory Card International Association slot to connect and can be added or removed as and when required.

Though the dial-up modems gave way to the more modern and high-speed broadband modems, as for the analog modems that you get even today, there are also other different types of modems available such as:

  • Cable modems
  • Cellular modems and
  • VoIP or Voice over Internet Protocol modems.

So you can choose one from any of these wide varieties of modems according to your needs or preference.

Advantages of a Modem

There are different advantages of using a modem today and these may vary according to the type of modem you chose to use.

However, the most common advantages are:

  • It is useful in creating a LAN or Local Area Network with the internet
  • It can transfer data at high speed which may vary according to the type of the modem
  • It helps in accurate signal conversion
  • It accepts instructions from other devices with its automatic dialing feature for establishing communication
  • If it comes with fax compatibility, documents can be sent or received instantly
  • It offers secure connection and
  • It can create several subnets.

However, there are a few downsides of using a modem as well that are quite worthy to know. These are:

  • Slower data transfer speed as compared to the hub
  • It does not allow connecting too many devices to it
  • It simply acts as an interface between internet and LAN
  • It does not offer traffic maintenance
  • It does not know the destination path
  • It can be relatively expensive than a router depending on the type you choose
  • If there are no firewalls built in, a modem can cause malware attacks
  • External modems lack mobility
  • Internal modems consume lots of power and are also often slower
  • DSL modems are not easily available especially in remote and rural locations and its service and performance depends mainly on the local phone company and
  • Connections can fail easily if the phone lines get disconnected.

However, today, high-speed digital modems are used more commonly.

In these specific types of modems the signals are much simpler and usually do not need to convert from analog to digital formats.


So, with almost everything that you need to know about the modems in a computer included and explained in this article, now you are surely more knowledgeable about these devices and the important role they play in establishing communication today.

You also know how it works.

About Taylor

AvatarTaylor S. Irwin is a freelance technology writer with in-depth knowledge about computers. She has an understanding of hardware and technology gained through over 10 years of experience.

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