The Sony WM-GX400 is a compact cassette player released by Sony that features a range of advanced options for its time. It incorporates a dual tape mechanism allowing for automatic reverse play, enabling uninterrupted playback of both sides of a cassette. The device is equipped with a built-in microphone for voice recording and playback capabilities, making it suitable for both listening to music and recording audio. The device often received praise for its portability and design, which made it a popular choice among users looking for a device they could easily carry. The user interface includes standard controls such as play, stop, rewind, fast forward, and record buttons. The WM-GX400 also features headphone output, volume control, and an auto tape selector, which adjusts playback characteristics based on the type of cassette used. In terms of sound quality, the WM-GX400 aims to provide a balanced audio experience with minimal distortion. The model typically operates on standard AA batteries, providing decent battery life for extended use. Its compact form factor made it suitable for use during travel, jogs, or casual listening at home.