microSD removable miniaturized Secure Digital flash memory cards were originally named T-Flash or TF, abbreviations of TransFlash. TransFlash and microSD cards are functionally identical allowing either to operate in devices made for the other. microSD (and TransFlash) cards are electrically compatible with larger SD cards and can be used in devices that accept SD cards with the help of a passive adapter, which contains no electronic components, only metal traces connecting the two sets of contacts. Unlike the larger SD cards, microSD does not offer a mechanical write protect switch, thus an operating-system-independent way of write protecting them does not exist in the general case. SanDisk conceived microSD when its Chief Technology Officer (CTO) and the CTO of Motorola concluded that current memory cards were too large for mobile phones. The card was originally called T-Flash, but just before product launch, T-Mobile sent a cease-and-desist letter to SanDisk claiming that T-Mobile owned the trademark on T-(anything), and the name was changed to TransFlash. At CTIA Wireless 2005, the SDA announced the small microSD form factor along with SDHC secure digital high capacity formatting in excess of 2 GB with a minimum sustained read and write speed of 17.6 Mbit/s. SanDisk induced the SDA to administer the microSD standard. The SDA approved the final microSD specification on July 13, 2005. Initially, microSD cards were available in capacities of 32, 64, and 128 MB. The Motorola E398 was the first mobile phone to contain a TransFlash (later microSD) card. A few years later, its competitors began using microSD cards. 2006–2008: SDHC and SDIO The SDHC format, announced in January 2006, brought improvements such as 32 GB storage capacity and mandatory support for FAT32 file system. In April, the SDA released a detailed specification for the non-security related parts of the SD memory card standard and for the Secure Digital Input Output (SDIO) cards and the standard SD host controller. In September 2006, SanDisk announced the 4 GB miniSDHC. Like the SD and SDHC, the miniSDHC card has the same form factor as the older miniSD card but the HC card requires HC support built into the host device. Devices that support miniSDHC work with miniSD and miniSDHC, but devices without specific support for miniSDHC work only with the older miniSD card. Since 2008, miniSD cards are no longer produced, due to market domination of the even smaller microSD cards. 2009–2022: SDXC The