What are Modems?  – Write a short note on modem. Describe is features.

Modem stands for modulation and demodulation. Modem is device that converts digital signal into analog and analog signal into digital. Modem sends and received data from one computer to another through telephone lines. The sending and receiving computers both must have modems.

The process of converting digital signal into analog signal is called modulation computer store data in digital form. Since a modem transmits data using telephone lines. So it is converted from digital to analog from.

The process of converting analog signal into digital signal is called demodulation. The modem on receiving computer receives data in analog form. The incoming analog data id converted back into digital format to be used by computer.

figure: data transmission by modem


Features of Modem

Some important features of modem are as follows:

1.  Speed: speed is the rate at which the modem can send data in bps. Typically modem speeds are 300 bps to 56bps.

2.  Self- Testing: Modem can teat the digital connection with computer. It can also test analog connection with remote modem.

3.  Voice over Data: Modem provides the facility of voice conversation while data is being transmitted. Both the source and destination modems should have this feature.

4.  Error Control: Modem use different methods to control errors for transmitted data.

What are different types of modems?

Different types of modems in terms of physical size and shape are as follows:

  1. External Modem

External modem is attached to the system unit as an external device through telephone line. It is connected to the telephone wall jack by another cable. External modem is connected to computer using serial cable to COM1 or COM2 port. It requires external power supply. It is easy to setup. External modem is expensive.



  1. Internal Modem

Internal modem is a circuit board that is inserted into an expansion slot on the motherboard. Internal modem cannot be moved from one computer to anther easily. It is difficult to setup than other types of modem. It is less expensive than external modem.



  1. Wireless Modem

Wireless modem transmits the data signals through air instead of cable. It also known as radio-frequency modem. It is designed to work with cellular technology and wireless local area networks.