What is a modem? What are different types of modem?

Modem stands for Modulator and Demodulator. It is a device that modulates signals to encode digital information for transmission and demodulates signals to decode the transmitted information.

A modem transmits data in bits per second (bps).

It is necessary for communication between digital devices and Analog devices.

Modem is necessary because it acts as a translator between the devices and rapidly transmits the information.

It converts the digital signal to Analog and vice versa to communicate between devices.

It encodes the signal and decodes at the other end and vice versa between the devices.

Building blocks of modem are shown in the diagram below −

Types of Modems

The different types of modems used to access the internet at home are as follows −

Telephone modem

A computer is connected through telephone lines to access the network of other computers. It is cheaper when compared to other modems because it does not have any installation cost and also the monthly fee of a telephone modem is low. It can be used in any house if a telephone network is provided.

Given below is the diagram of telephone modem −

Digital subscriber Line

It provides high speed internet connection through telephone lines. It is expensive when compared to a telephone modem. The DSL is also connected with phone lines similar to telephone modem, but the difference is in DSL voice communication and internet service is used simultaneously whereas in telephone modem it is not provided.

Given below is the diagram of digital subscriber line (DSL) −

Cable modem

Cable Modem is a device that allows high-speed data access via a cable TV (CATV) network. Most cable modems are currently external devices that connect to the PC through a standard 10 BASE-T Ethernet card and twisted-pair wiring.

Given below is the diagram of cable modem −

Satellite modem

It is a device that provides internet connection through satellite dishes. It transfers the input bits to output radio signals and then executes vice versa. It is costlier when compared to all other modems but provides better reliability to the internet network.