I’ve you ever wanna try something fun, scan some frequencies that are assigned to local utilities. Sometimes you might happen upon some signals that sound like an old modem. It might surprise you to learn that some of these are actually modems that are transmitting data via analog signals. If you hook up the audio out from your scanner to the audio input on your notebook you can utilize various programs decipher or decode those transmissions. Below is a screen shot of a scanner program doing just that. The information that is in hex which would need to be converted to ascii to make it human readable.
Since I was not an intercept operator I don't know anything about this stuff.