WM-20

Miniaturization had already become a Walkman trademark, but the WM-10's telescoping form still felt like a first draft. Six months later the WM-20 delivered the fully realized version, adding Dolby B, metal-tape support, and a sturdier mechanism while keeping the same retracting architecture.

The internal layout used surface-mounted parts and a single cleared edge to make room for the sliding frame, letting the body collapse to the outline of the cassette inside it and extend into a slim, conventional player for use. Weight stayed around 190 grams, and the diagonal control arrangement made one-handed operation easy at a time when portability shaped daily listening.

A single AA cell powered roughly fifteen hours of playback. Frequency response reached 40 to 15,000 hertz, with Dolby B reducing background noise and a selector handling normal, chrome, and metal tape.

Compared with the WM-10, the mechanism felt more certain in motion, and the telescoping action locked into place with the precision expected from Sony's early-eighties engineering. Marketing leaned on the simplicity of the idea.