You must have heard Modem’s name before. But do you know in the right form what Modem is, 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.
However, NIC Modem is used to integrate with the computer motherboard. Rather it is available as a separate part that can be installed in PCI slots which you can find in the motherboard.
A modem is not required much in LAN, but it is needed in other internet connections like dial-up and DSL.
Types Of Modems
There are many types of modems that different from each other in Speed and Transmission rate.
- Standard PC modem
- Dial-up modems
- Cellular modem
- Cable modem
- DSL Modems
| Types of Modems | Details |
| Standard PC modem | Normal Modem That We See In Our Day to Day Life |
| Dial-up modems | It has a 56Kb data Transmission speed. |
| Cellular modem | It used on the laptop and enables it to connect at the same time |
| Cable modem | Which is 500 times faster than a standard modem |
| DSL Modems | DSL Modems are also very popular. |
So today I thought that why should you people explain what Modem is in English 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 devices, 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 an 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 connect with the 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 the 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 that 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.
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 or Data Over Cable Service Interface Specification.
That 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 a 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, 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 the analog signals of a computer network are converted into digital signals in 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 ends. 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.
Also, 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 wake-up 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 the 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 data is easily transmitted.
To complete this process, these signals are sent to different pins in the plug 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 ranges. Therefore 3$ 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 analog 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 it is reversed in a series of smooth curves.
On the other hand, computers can only understand 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 an 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 transmitted 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, so this device is called Modem.
One thing that 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, 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 big such as pictures, sound, and video sequences that 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 them.
Categorization following basic modem features:
1. Directional capacity: half-duplex modem and full-duplex modem.
2. Connection to the line: 2-wire modem 4-wire modem.
3. Transmission mode: asynchronous modem synchronous modem.
Half Duplex 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 to DTE which is done in its own digital interface via a control signal.
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.
Two-Wire And Four Wire Modems
The line interface of these modems can be either a 2-wire connection or a 4-wire connection, in the transmission medium.
Two-Wire
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 this 4-wire connection.
3. As the physical transmission path is different for each direction, the same carrier frequency is used in both directions.
Four-Wire
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 is 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 a 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 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 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 that are transmitted and received.
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 as 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 a 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 the backend, so they are hidden from users, but they work from the backend itself and make our life 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 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 restaurants, movie theaters, retail stores
Train Stations Ticketing machines, bus stations, 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 controlled remotely only with the help of a 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 the alert.
4. Safe company – the ability to check the temperature.
5. The irrigation system of the 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 locations send data on a daily basis to that HQ.
Dial-up modem solutions are very ideal because they can be programmed to send data every day with secure connections. 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 Communication
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.
Example
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 circuits
3. Gasoline vapor containment system
4. 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.
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