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Modem

Modem (Modulator-Demodulator)

A modem is a device that modulates an analog signal to digital information. It also decodes carrier signals to demodulates the transmitted information.
It is a hardware component that allows a computer or another 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 digital data (1s and 0s) that a computer can recognize. Similarly, it converts digital data from a computer or other device into an analog signal that can be sent over standard telephone lines.

The main aim of the modem is to produce a signal that can be transmitted easily and decoded to reproduce the digital data in its original form. Modems are also used for transmitting analog signals, from Light Emitting Diodes (LED) to radio.
A modem is a device that connects your home, usually through a coax cable connection, to your Internet service provider (ISP), like Xfinity. The modem takes signals from your ISP and translates them into signals your local devices can use, and vice versa.
  • A modem is a device that modulates an analog signal to translate digital information.
  • Convert the data (0s and 1 s) into an appropriate analog signal.
  • A modem operates on the Datalink layer.
  • Modem brings in the requested information from the internet to your network.
  • Modem does not help to examine the data packet.
  • A modem is used for accessing the internet as it connects your computer to the ISP.
A Wi-Fi modem is a single device that combines the functionality of a modem and a router, making it a one-stop shop for Internet connectivity. A Wi-Fi modem is a single combined device that translates Internet data packets via the modem and sends it through wirelessly to devices in your home via the router.

Types of Modems : Modems can be of several types and they can be categorized in a number of ways.
Dial-up Modem: This type of modem are using the analog telephone line to connect two end devices like two personal computer. It offers an interface between the digital system and an analog system. It modulates the binary data into the carrier signal on the telephone line. Dial-up modems use a cable that connects to your phone line.

DSL Modem: DSL model uses twisted pair cable for transmission of signals. It will radiate at higher frequencies and covered more distance than the dial-up modems. It offers to speed up to 2 Mbps and even more, which depends upon the type and configuration.

Cable Modem: This type of modem is designed in a way to carry radio and television signals. It can be configured internally/ externally with the television line to convert the signals into the compatible mode.
A cable modem uses coaxial cables that connect to the back of the modem and the bolt-like outlet in your wall or on your cable box. This type of modem delivers high speed internet to your device.

Wireless Modem: It is also called a radiofrequency modem. These are designed to work with cellular technology and wireless local area networks. These are not yet perfected but the technology is rapidly improving.

Internal modem:
- Modem that connects to a PCI slot inside a newer desktop computer, or ISA slot on an older computer. The internal modem shown above is an example of a PCI modem.

External computer modem
External modem - Modem in a box that connects to the computer externally, using a serial port or USB port. The picture is an example of an external USRobotics modem.

Half Duplex Modem: This type of modem allows you to transmit a signal in one direction at one time. So, if the modem is receiving the incoming signal, then it displays indication light to the sending point to stop transmitting data till the time it completes the process of receiving signals.

Full Duplex Modem: This type of modem permits transmission in both directions at the same interval of time. These types of modems have two carriers on the line.

Two-Wire Modem: This type of modem uses a pair of wires for both incoming and outgoing carriers. However, if we are using the half-duplex mode, then the same frequency can be used for transmission as data flows in the same direction only at a time.

Transmission Rate:
It includes how many bits per second a modem can transmit or receive.

Speed: The speed of the modem is determined by the modulation and demodulation standard.
The rate at which a modem converts digital signals into analog signals and sends them over transmission media and modem Converts analog signals into digital signals is called modem speed.
It is measured in bits per second (bps).
Different modems have different speeds : 2400 bps, 9600BPS, 56.5KBPS

Source: Few websites, Wikipedia...

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