In 1979, Sony released the TPS-L2, which enabled personal stereo playback using headphones. The combination of a lightweight, portable design and cassette playback functionality established the basic configuration for portable music playback.
TPS-L2
The TPS-L2 is a playback-only Walkman. It features two headphone outputs and a hotline function, and uses AA batteries. It has a configuration unique to early Walkman models, designed for shared listening.
In 1979, the basic structure of the Walkman was established as a product. This structure was continued to be applied to subsequent product designs, but configurations that relied on the cassette format were also maintained.