what is a modem? & types of modem? If You Find The Answer Of These Question Then This Article Is Definitely For You. In This Article We Will Discuss About what is a modem? types of modem, Functions Of Modem, And Different Functions Of Modem. So Without Wasting Time Let’s Know About The modem.
what is a modem?
The modem stands for Modulator / Demodulator. A modem is a contraction of a two-word modulator and a demodulator, a modem commonly used to send digital data to a phone line. Sending a modem modifies the data into a signal that is compatible with the phone line. And demodulates the received modem signal back into digital data. Wireless modems convert digital data into radio signals and back.
A modem is a device or program that allows computers to transmit data, as an example, telephones or cable lines. Computer information is stored digitally, while the information is transmitted over telephone lines as analog waves. A modem converts between these two forms. Modems came into existence in the 1960s, allowing terminals to connect to computers over phone lines. A specific arrangement is given below:
In such a configuration, a dumb terminal at an off-site office or store can “dial” into an oversized, central computer. The 1960s was the age of shared computers, so a business often purchased computer time from a time-sharing facility and connected it via a 300-bit per second (bps) modem. A dumb terminal is just a keyboard and a screen. At that point, a really common dumb terminal was called the DEC VT-100, and it became a type of the day. The VT-100 can display 25 lines of 80 characters each. When the user typed a personality on the terminal, the modem sent the ASCII code for the character to the pc. the pc then sent the character back to the pc in order that it might appear on the screen.
When personal computers started appearing within the late 1970s, the Bulletin Board System (BBS) became the craze. One person will start a computer with a modem or two and a few BBS software, and others will dial in to attach to the bulletin board. Users will run a terminal emulator on their computer to emulate the dumb terminal. People got along at 300bps for an extended time. This speed was tolerable because 300 bps represents about 30 characters per second, which may be a lot more characters than someone typing or reading a letter.
Once people started transferring large programs and pictures from the bulletin board system, however, 300bps became unbearable. Modem speeds went through a series of stages at approximately two-year intervals:
- 300bps – through the 1960s 1983 or so
- 1200bps – gained popularity in 1984 and 1985
- 9600bps – First introduced in late 1990 and early 1991
- 19.2 kilobits per second (Kbps)
- 28.8 Kbps
- 33.6 Kbps
- 56 Kbps – became standard in 1998
- ADSL, with a theoretical maximum of up to 8 megabits per second (Mbps).
types of modem
Different types of computer modems keep everyone connected via Internet technology, wherever they may be. The modem, MOdulator, is a shortened form of DEModulator, which allows computers to convert data into useful information. When it receives analog data through a connection, it must convert it to digital data to be usable by the computer. Similarly, it reverses the action when it has to send data. It is not so important, here, to know how modems work but it is necessary to distinguish between different types of computer modems
Internal computer modem:
Some computers have an internal modem which may be a built-in modem or a PC card modem. For a PC card modem, a PCI slot or even an occasional ISA slot is required, depending on the available interface your motherboard uses to get the modem.
The internal computer modem is accessed via a pair of RI-11 connections with a dial-up Internet connection. Also called copper telephone lines, the RI-11 allows computers to receive and send data as described above. Internal computer modems are typically 56K modems, which means that the modem is capable of receiving 56 Kbits / s (56 kilobits or 56000 bits per second) of data. Such data transmission is called downstream transmission, came from a provider, and is transmitted over telephone lines.
This is usually the standard with Internet Internet and web technology bandwidth telephone lines. However, because the Internet is a two-way system that must also flow from the client to the (server) provider. For this purpose, the computation can use 56K modem V90. The upstream transmission rate, on the other hand, is capable of providing a 56K modem V 92 48 transmission rate, to flow 33.6 Kbit / s.
This is another word that we have to consider different types of computer modems. An external modem can be used for the same purpose and in minimal conditions as an internal computer modem. An external modem, however, is a small box with other types of interfaces to connect to the computer.
It can be a serial modem named as such because it uses a serial port to connect to the computer. Typically installed on the back of a computer, the serial port is an easy-to-install alternative to an external modem. The same small box, on the other hand, can be a USB modem that uses a USB port usually placed behind or in front of the computer. 10 Kbits / Upstream Firstly the external modem may be a dial-up modem but is more expensive than the internal as well as another type of external modem. You can consider two important types of modems: cable modem and DSL modem. You are high-speed Internet services.
All ISPs. Usually in broadband packages supply a special modem called a digital modem, it is important to notice that the cable modem has to connect to an Ethernet card, which is placed on the computer PCI slot to provide the broadband internet concept to the user. This is true if you choose to use an Ethernet connection. However, if you get the option to use USB connection then you will not need it.
A cable modem uses a coaxial cable television lines to provide more bandwidth than a dial-up computer modem. Much faster access to the web is providing upstream transmission of up to 38 Mbit / s with downstream transmission by cable modem and up to one Mstream / s. Unfortunately this transmission rate is shared due to fluctuations with the number of users on which the cable technology is based * DSL modem: DSL (Digital Subscriber Line) modem specifically for the user to use for connection to a telephone switching office. is done. This technology, available and sometimes usable, is split into two main categories: ADSL (Asymmetric Digital Subscriber Line) is employed in North America and it’s downstream transmission rates from 1.5 Mbit / s to 9 Mbit / s and Supports up to 3 Mbits / s. Upstream transmission rate. SDSL (Symmetric Digital Subscriber Line) is used in Europe and has the same data rate for downstream and upstream transmission which is 128 Kbits / s.
Another category of modems
In addition, modems are classified based on various criteria such as the place where they are installed, the way they accept information, and the way they transmit signals. Based on these criteria, modems are divided into the following types:
Internal and external modems:
Internal modems are in the form of circuit boards, which fit into the expansion slots of the motherboard. External modems are attached separately to Internet Basics 11 cases and not inside system units. The modem is connected to the computer anchored telephone line through two separate cables.
Intelligent and standard modems:
Standard modems accept instructions from the keyboard of a microcomputer. Intelligent modems respond to commands and simultaneously transmit information, this is done with the help of microprocessor chips.
Wireless and short-haul modems:
Short-haul modems transfer data via cable. Since they do not require an external power source, they are also called modern eliminators. The wireless modem does not require any kind of cable to transmit the data signal.
How does MODEM work?
A computer sends information within the sort of a digital signal. But information on telephone lines must be transmitted as an analog signal. to resolve this problem, the functionality of a modem comes into play. It converts digital signals into analog signals. These analog signals are carried over telephone lines. When these signals reach another computer, the analog signals are converted back to digital form by their modem.
functions of Modem
A device that performs two important functions of modifying and collapsing analog signals is called a modem. Analog signals encode digital information at the time of modulation and decode it back during demodulation to transmit data. Modulation is the process of changing the form of a signal carrying information. The demodulation process works to extract information from signals that are modulated. Analog signals can be transmitted using devices such as radios or diodes. Modems are classified based on two criteria
* Data is sent per unit time.
* Changes in signal position per unit time
Modems were first used in the 60s to connect computers to a network of telephone lines. The period is also known as the age of time-shared computers, as computers had to purchase time to connect to the network via a modem, with speeds of up to 300 bits/second.
different functions of modem
In addition to converting digital signals into analog signals, modems perform many other functions. The modem minimizes the errors that occur during the transmission of signals. They also have the functionality to compress data sent through signals. The modem also serves to regulate the information sent over a network.
* Error Correction:
In this process, the modem checks if the information they received is unpublished. The modems involved in error correction divide the knowledge into packets called frames. Before sending this information, the modem tags each frame with a checksum. A checksum is a method of checking redundancy in data on a computer. The modems receiving the information verify whether the error sent by the rectified modem matches the checksum. If it fails to match with checksum, the information is sent back
* Compressing Data:
To compress data, it is sent together in multiple bits. The bits are grouped together by the modem so that they can be compressed.
* Flow control:
Different modems vary in their speed of sending the signal. Thus, it causes problems in receiving signals if either one is dim. In the flow control mechanism, the slower modem sends a faster signal to pause, sending a ‘character’. When it is ready to catch up with the rapid modem, a different character is sent, which resumes the flow of the signals.
Conclusion of what is a modem? & types of modem
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Source: I&WT, Wikipedia
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