WM-701C

Fitting a full cassette transport into an 18.2-millimeter enclosure required a new internal layout, and the WM-701C introduced that approach in one of Sony's smallest bodies. It used an EX Amorphous playback head, Dolby C noise reduction, and a compact, electronically controlled mechanism designed to work inside such a thin frame.

To make the enclosure this slim, Sony replaced many of the usual moving parts with small electronically triggered components and arranged the interior to use every bit of space. A compact power circuit let the player run from a single gumstick battery, which further supported the thin layout.

The transport sat on a metal base to keep it steady, and the circuit boards folded through the body like layered paper. Even with its small size, the Walkman felt solid because everything inside was packed tightly.

The WM-701C showed how far Sony could push miniaturization before the design introduced practical limits. Sony followed it with the WM-703C, which added rapid charging, and the WM-702, which used thicker panels and a different audio system.