In the late 1970s, two graduate students at Duke university were trying to come up with a better way to connect computers at further distances. They wanted to share what was essentially bulletin board material then a light bulb moment went off. They realized the basic infrastructure for this already existed, the public switched telephone network. or PSTN.

Plane Old Telephone Service POTS

These Duke grad students weren’t the the first ones to think about using a phone line to transmit data. But they were first to do it in a way that became somewhat permanent precursor to the dial-up networks to follow.

The system they built is known as the Usenet and a form of it is still in use today.

Transferring data across a dial-up connection is done through devices called modems. Modems stands for modular demodulator and they take data that computers can understand and turn them into audible wavelengths that can be transmitted over POTS. conceptually similar to how line coding is used to turn ones and zeros into modulating electrical chares across ethernet cables.

Early modems had very low baud rate. A baud rate is a measurement of how many bits could be passed across a phone line in a second. (about 110 bits per second.)

By the time Usenet was being developed, this rate had increased to around 300 bits per second. and by dial-up 14.4 kilo bits per seconds.