Definition of modem
“A modem is a network device that converts digital signal from computer to analogue signal and converts analogue signals to digital signals”
A modem is a short form of modulator and demodulator.
Data transfer in analogue form in the telephone cables. There are different cables like coaxial cable and twisted pair cables. In these cables data travels in analogue form. And our computer understands digital data. So to convert analogue data to digital form and digital data to analogue form we need a network device. This network device is known as a modem.
History of modem
The modem was invented in 1996 by a Canadian electrical engineer whose name was Brent Townshend.
The idea of the first-generation modem was in the 1950s and was used by the American defence system.
In the 1980s full-duplex modem was introduced by CCITT.
Types of modem
There are some types of modems that include:-
Dial-up modems
This type of modem has a slow transfer speed. It uses telephone lines. When the connection is made from the modem to the internet then the phone line becomes busy and you cannot receive/dial a call. It is mostly used in rural areas where wired and wireless internet is not available. After the connection is made from the modem then it charges the price of one telephone call. Dial-up modem uses modulation and demodulation technique.
Modulation: Converting digital signal of the computer to analogue signal is known as modulation.
Demodulation: Convert the analogue signal of cables to a digital signal is known as demodulation.
Dial-up modems have a data transfer speed of up to 56 Kbps.
Dial-up modems are of two types. One is an internal modem and the other is called an external modem. Internal modem is attached to the motherboard and it is difficult to install an internal modem as you have to open the CPU case. While external modems are not attached to the motherboard.
Digital modem
A Digital modem is also known as a broadband modem. Digital modem has some types:-
- DSL modem
- ISDN modem
- Cable modem
A DSL modem is used to transfer data in DSL cables. A DSL modem is attached to the telephone line on one side and attached to a computer on another side. It provides high data transfer through a telephone line. DSL is a shot form of a digital subscriber line. It is easy to install.
You can use both telephone line and the internet at the same time. You have to get internet from the ISP provider to use the DSL modem. If you live close to ISP (internet service provider) then the DSL modem gets you high internet speed.
ISDN modem is also an external device. It is used to make calls and connect to the internet.
A cable modem is used to connect to the internet by using a CATV network. It is a broadband modem. The CATV providers give you a cable splitter that can split the cable into two cables. One cable goes to the TV and the other cable goes to your cable modem for internet connection.
Wireless modem
A wireless modem is also known as a radiofrequency modem. These modems make a wireless connection from your device to the ISP provider. It can be used on smartphone, laptop and desktop computers.