WM-F51

The WM-F51 is the radio-equipped counterpart to the WM-51, combining the same retractable earphone storage system with cassette playback and a built-in tuner covering FM, AM, and TV audio bands. Auto-reverse, Dolby B noise reduction, and a hold lock remained part of the cassette side, while the slightly thicker body made room for the tuner circuitry without losing the compact, self-contained form. Power came from either a single AA battery or the includes rechargeable cell and charger.

This is exactly the kind of extension Sony was good at once a useful format had been established. The retractable design had already solved a real portability problem, so adding radio simply made the concept more complete for people who wanted one compact machine to cover both personal tapes and whatever happened to be on the air. It is not a dramatic model, but it is a very coherent one.