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What is modem?

Updated on January 15, 2010


The device that converts digital signals into analog signals and analog signals to digital signals is called Modem. The word modem stands for modulation and demodulation. The process of converting digital signals to analog signals is called modulation. The process of converting analog signals to digital signals is called demodulation. Modems are used with computers to transfer data from one computer to another computer through telephone lines.

Modems have two connections these are.

  • Analog connection
  • Digital connection

Analog connection.

The connection between the modem and the telephone line is called analog connection

Digital connection

The connection of modem to computer is called digital connection



  • Internal modem
  • External modem


It fits into expansion slots inside the computer. It is directly linked to the telephone lines through the telephone jack. It is normally less inexpensive than external modem.Its transmission speed is also less external modem.


It is the external unit of computer and is connected to the computer through serial port. It is also linked to the telephone line through a telephone jack. External modems are expensive and have more operation features and high transmission speed

Main Features of Modems

The modems have several features. These are:


The rate at which modem can send data is called speed of the modem. It is measured in bits per second (bps). Typically modem speeds are 300 bps to 56 K bps.

ii. Self Testing

Internal programs or firmware are provided in modems that check digital and analog connections of the modem. These programs also check internal electronics of the modem. These programs are called self-testing programs. Self-testing programs ensure accurate data transmission by the modem.

iii.Voice over Data

Modem modems also allow voice conversation while data is being transmitted. This requires both the source and the destination modem to have this feature.

iv.Synchronous or Asynchronous Transmission

Modem can have either synchronous or asynchronous transmission. Usually modem transmission is asynchronous.


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      Rasel 5 years ago

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