The Music of Modems

You probably remember using your first computer. And if you are at least 25 years old, you probably also remember that at one time you had to connect to the internet through a modem. Modems were designed to allow you to send data over a network that was designed to only carry voice transmissions. Therefore, the communication method between two modems had to use sound within the audible hearing range or the data would not get carried on the phone line. Today, of course, our digital phone systems (DSL) can carry both voice and data at the same time.

But with a modem, when you initiated the connection to the internet there was “the sound”. It was noticeable, memorable and rather grating. The reason it played out loud is so that you could hear if something went wrong with the connection such as a busy signal, or a wrong number.

But what was that sound? Typically 20-30 seconds long, it was a choreographed sequence of audible data, fed through the phone line in a very specific order, that connected you to the larger online world. It included all the information that the receiving modem needed in order to facilitate communication with the modem making the connection request.

At that time, phone lines only carried the small range of frequencies in which most human conversation takes place – somewhere from 300 to 3,300 hertz. The modem had to work within those limits in order to carry data across phone lines.

The frequencies of the modem’s sounds represent the basis for further communication. Early modems, for example, would play a note that meant, “I can go this fast.” Depending on the speed the modem is trying to talk at, this tone will have a different pitch.

So, those sounds weren’t just a sign that data was being transferred, they were the data being transferred.

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