MODEM

The main function of modem is to convert the digital to analog signal(modulation) and analog to digital signal (demodulation) for the communication between the server that provides the internet and the computer which uses those data. Modem stands for modulation and demodulation.

TYPES OF MODEM :

External Modem: This is a modem separated from the system unit in the computer case. It is connected to the serial port of the computer by means of a cable. It is connected to the telephone  jack by another cable.

Internal Modem: An internal modem is a circuit board that can be added to the system.

Standard Modems: Most modems used today are  standard modems. These modems are usually operated by commands entered from a  keyboard. Users control the functions a modem through the keyboard. Modems may use different command languages to control their functions, but most modems (called "Hayes compatible") use a popular language developed by a company "Hayes Microcomputer Products, Inc." The command ATDSX4, for example, indicates that pay attention (AT), dial stored telephone number (DS), and then display the progress of the call (X4).

Intelligent Modems: Intelligent modems are also called advanced modems. These modems can accept new instructions and then respond to the commands while transmitting data and information. These can be done by microprocessor chips and internal read only memory (ROM) contained in the modem. Of course, these modems are more expensive.

Short-Haul Modems: Short- haul modems are devices that transmit signals through the cable . They are also are called modem eliminators, because they do not require an external power source. They are also called line drivers that can send data for a distance of more than one mile. This type of modem can be used within or across several buildings in a company or a university campus.

Wireless Modems: Wireless modems transmit the data signals through the air instead of by using a cable. They sometimes are called a radiofrequency modem. This type of modem is designed to work with wireless local area networks namely wifi.

Even in the cell phone that we use today has modem the modems are used for surfing in the internet etc.This modems also does the same work of modulation and demodulation but the circuit of this modem is much smaller than the normal modem