Secure Digital (SD) cards are removable memory storage cards about the size of a postage stamp. They are used in portable devices such as digital cameras, cell phones, personal digital assistants (PDAs), and mobile computers. A Bluetooth® SD card, also called a Bluetooth® SDIO (In/Out) card, is a device that combines the SD format with an In/Out device — in this case, a Bluetooth® modem. The modem utilizes the SDIO card slot to create a Personal Area Network (PAN). This minimalistic format is more convenient for slimline devices than using a USB Bluetooth® adapter, even when the product can support either.
A Bluetooth® PAN is very handy for connecting personal devices across relatively short distances. Class 1 Bluetooth® broadcasts up to about 328 feet (100 m), while Class 2 has a range of about 33 feet (10 m). Bluetooth® uses radio frequency (RF) signals and therefore does not require line of sight. Broadcast radius can be reduced by various factors, however, including certain types of building materials, interference or weak batteries.
One can use a Bluetooth® SD card to transfer pictures, movie clips, songs or data between digital cameras, cell phones, PDAs, or computers. It can also be used to synchronize calendars or email between devices, or to send print jobs to a local printer. Up to seven devices can join a Bluetooth® network, allowing housemates or siblings to exchange instant messages, play games, or engage in other networking activities. A Bluetooth®-enabled cell phone with Internet access can extend access to a connected device using an SD card.
The great advantage of Bluetooth® is that it is very easy to establish a network and sharing. To enable sharing over other types of networks requires extensive configuration of the operating system and resources, fit only for administrators or those familiar with networking protocols. Bluetooth® also uses encryption, keeping shared data safe as it travels between devices.
The Bluetooth® specification continues to evolve, thanks to the Bluetooth® Special Interest Group (SIG). As of 21 April 2010, SIG finalized version 4.0, which includes low energy protocols for greater power-saving performance. Like all versions, 4.0 is backward compatible with previous flavors and incorporates their benefits.
When shopping for a Bluetooth® SD card, consumers should check to see which version it supports. Products that support the latest version might cost a little more, but the benefits are usually worth the extra cost. Shoppers should also confirm that the card is compatible with the device or devices in which it will be used. The device must be SDIO-compatible; an SDIO card inserted into a slot that is not compatible will not cause harm, but the card will not function. SDIO slots support both SDIO devices and SD memory cards.