Andrew Kim of Minimally Minimal got his hands on an original Sony Walkman and provides an interesting look back at a seminal piece of personal technology. Initially, the Walkman was billed as the “Walking Stereo with Hotline”:
Next to the dual headphones is a button labeled “Hot Line”. This was another key feature of the TPS-L2. When the user pressed the Hot Line button, the device would would override the music with audio from the built in microphone. It allowed you to listen to Subway announcements or talk to a friend without taking off your headphones. I find it to be a particularly clever idea as it uses existing parts from tape recorders. Hot Line wasn’t really a sought after feature though, and was axed in later models.