How do Dial-up Connections Work?

A standard telephone line (often called a POTS or Plain Old Telephone Service line) uses an analog signal to transmit audio information from your home or office to the local telephone company Central Office (often called a CO). There, the copper wire from your house is terminated in a set of special machinery that allows the audio signal from your house to enter the Public Switched Telephone Network (PSTN) where it is routed to the person or company that you are calling.

A regular dial up modem, modulates a digital signal from your computer into an analog signal that can be easily transmitted over the regular telephone network, and then gets demodulated by special modems at EasyStreet. This modulation and demodulation process is the process that causes the 'weird screaming' that you always hear at the beginning of a dial-up Internet connection, and it is where the term modem comes from.

Because regular analog modems are restricted to the voice telephone network, they only use a small portion of the available bandwidth that could be transmitted over your copper phone line. The maximum amount of data that you can receive using an ordinary modem is determined by the quality of your phone line, but it is generally restricted to between 30-45 kbps.