J-Phone
J-SH51

The J-SH51, manufactured by Sharp for J-Phone, was a landmark device in mobile history, primarily remembered as the world’s first mobile phone to feature a Secure Digital (SD) card slot. While the Siemens SL45 had introduced expandable memory via MultiMediaCards (MMC) two years earlier, the J-SH51’s adoption of the SD format set the standard for high-capacity removable storage that would eventually dominate the industry. Launched in March 2002, the J-SH51 was part of J-Phone’s high-end "5x" series, designed to showcase the carrier’s most advanced multimedia services. The inclusion of the SD slot allowed users to move beyond the limited internal memory of the time, enabling the storage of high-quality photos, Java-based games, and—most notably—music and video. It supported the playback of MPEG4 video files and AAC/MP3 audio, effectively turning the mobile phone into a portable media player. The device featured a 2.0-inch GF colour LCD capable of displaying 65,536 colours, which was among the best in the market at launch. Its camera was also a significant step up from the early 110,000-pixel sensors found on the J-SH04; the J-SH51 boasted a 310,000-pixel CCD sensor, providing much sharper images for J-Phone's "Sha-mail" (Photo Mail) service. This was further aided by a built-in "Mobile Light" to assist with low-light photography. Architecturally, it was a classic Japanese clamshell of the era—tall, narrow, and featuring a prominent external antenna. It also supported "J-Sky" (J-Phone’s mobile internet service) and "Java" applications, allowing users to download sophisticated games and utilities.