Explain the Concept of MODEM and Types of MODEM

Modem is abbreviation for Modulator – Demodulator. Modems are used for data transfer from one computer network to another computer network through telephone lines.

The computer network works in digital mode, while analog technology is used for carrying massages across phone lines.

Modulator converts information from digital mode to analog mode at the transmitting end and demodulator converts the same from analog to digital at receiving end.

The process of converting analog signals of one computer network into digital signals of another computer network so they can be processed by a receiving computer is referred to as digitizing.

Modulation and Demodulation

Modems can be of several types and they can be categorized in a number of ways.

Categorization is usually based on the following basic modem features:

  1. Directional capacity: half duplex modem and full duplex modem.
  2. Connection to the line: 2-wire modem and 4-wire modem.
  3. Transmission mode: asynchronous modem and synchronous modem.

Categories of MODEM


  • External modem
  • Internal modem

Any external modem is attached to any computer has an RS-232 port. An internal modem comes as an expansion board that can be inserted into a vacant expansion slot.

Types of MODEM


  1. Digital cable modem
  2. ISDN modem
  3. Digital subscribes line modem
  4. Satellite modem

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