Dial-up is a way of accessing the Internet with the help of a telephone line and a modem. The telephone line is connected to the modem, which in turn dials the number of the Internet Service Provider (ISP) to access the Internet. Most ISPs have a set of local or national numbers that users can dial to get connected to the Internet. These are known as the dial up access numbers.

Dial-up is popular, because all it requires is a computer with a modem and a telephone line. It is not as fast as broadband, but it is preferred due to easy availability and a low installation cost. Internet users can choose to pay their ISPs monthly or yearly. However, the call-charges add considerably to the cost. If the calls are charged on a fixed time basis, the cost is higher.

A modem is a device that sends digital data over a phone line. It is a short form used for modulator-demodulator (mo+dem). In order to dial the dial up access number, the telephone line must be connected to the modem.

The modem connects to the dial up access number provided by the ISP. It sets up a username and password and sends it to the server. Once the connection is made, a handshake takes place. This means data is exchanged between the modem and the remote server. Based on the information provided, access is granted to the Internet.

The dial up access numbers provided by the ISPs can be either local or national, or both. Generally they are local numbers since calling long distance is expensive.

Generally, the ISPs themselves provide all the information regarding the access numbers. The Internet can also be searched to find access numbers for any particular area. Still, it is best to confirm with the respective ISP whether the numbers are local or national.