Understanding the Data Transfer in Dialup Connection

The main advantage of dial up connection is that it could be connected through telephone lines. A modem used as the connection device between a computer and the telephone line through which you connect to internet. The modem sends and receives data over the phone line. Here we try to elaborate the process of data transfer in a Dial up connection.

For an ordinary internet user, a modem is device that lets your computer to internet through a standard telephone. However, many people are not aware as exactly why a modem must be used to connect to internet in a dialup connection. The reason for introducing a modem between the phone line and computer is that that the phone lines transmit data in analog form and the data on internet transmits in digital form. Hence, the main function of the modem is to make both sides happy by providing data in the form they could process or transmit.

The process of transferring data over the phone line is much like telephonic conversation between two people. Here, the modem replaces the people on both sides. The modem has two ends one connects to the computer and other one to the telephone line. When you try to makes a connection, the sending modem modulates the data into a signal that is compatible with the phone line, and the receiving modem demodulates the signal back into digital data. The screeching sound that comes when modem connects to the internet is due to the initial connection process and modem’s conversation with the central computer to establish the connection. The rise and falls in the tone of that sound is due the conversation of digital data (in os and 1s) into analog data. The higher pitched tone represents the digit 1 and a lower pitched tone to represent the digit 0.

The above description is just an overview of the data transfer in a Dial up connection. The Actual process is a much more complex than sending and receiving signals in one direction and then another. There are many other factors involved in it. For example, most modems simultaneously send and receive signals in small packets. The modem should be able receive and send data simultaneously. This is important to gain the speed of the data transfer. It is also equally important to send and receive data properly in the actual for without losing its integrity.

To negotiate above requirements, modems transfer data in small packets called bits. Modems compress digital signals before modulating them. It allows them to send the data in a way that it can travel along telephone lines more efficiently. The receiving modem can then decompress data after demodulating the signals. To check the integrity, the modems add a code at the end of each data packet called checksum. It allows both terminals to know if the data packets are transmitted in correct order. If the code does not match then the sending modem resends the missing segments of data completing the data transfer.