Sony’s compact — at the time — TPS-L2 was the world’s first portable cassette player, forever changing how people listened to music. This device hit Japan in 1979, priced at a hefty $288. It featured a “hotline” button, which allowed users to talk over the music via built-in microphone — overriding the cassette sound, stereo playback, and dual headphone jacks. Many lower-priced clones soon followed within two years. Video after the break. Click here for more pictures.