By Ashish Dwivedi

SDHC (Secure Digital High-Capacity) are new Flash memory cards based on the SDA (Secure Digital Association) 2.00 specification. SDHC provides removable memory storage for compatible digital devices, including cameras, camcorders, PDAs, MP3 players and more.SDHC cards guarantee a minimum sustained data transfer speed, not a maximum speed. There are three available speeds – Class 2, Class 4 and Class 6.There is difference of Data Transfer Rate (DTR) between these classes.

Class 2 devices guaranty a minimum DTR of 2 MB/sec
Class 4 devices guaranty a minimum DTR of 4 MB/secClass 6 devices guaranty a minimum DTR of 6 MB/sec

The device class is specified on the device itself.

The previous versions of SDA specifications did not provide such common standards for sustained data transfer speeds to be shared by all manufacturers. The new speed classification allows users to select card performance based on the needs of particular applications, such as HD video, and other MPEG applications, rather than just a maximum speed rating.

SDHC Cards comes in different capacities ranging from 4 GB-32 GB. Please see the highest capacity supported by your device. SDHC logo on your device does not neccesarily means that your device will support all the capacities that are provided under SDHC cards. There is probabilty that your camera may support only 4 GB of capacity which is also SDHC. Please contact your device manufacturer or refer to your manual for further clarifications.

SDHC cards has the same physical size as SD cards but with higher capacities which cannot be used with SD host devices that do not comply with SDA Specifications Version 2.00.It makes sense,since the same size card with increased capacity would have a different circuit design all together. Also, there is a Sandisk Card Reader that can start supporting SDHC cards after a small firmware upgrade. But only few device versions of that particular model can be upgraded to support SDHC Cards.Host devices complying with SDA Version 2.00 can use both SD Memory Cards and the new SDHC Memory Cards.

Current SD cards complying with Version 1.01 and Version 1.10 use either the FAT16 file system, whereas Version 2.00 uses FAT32. This latest specification was established to support SDHC card applications with higher capacity needs.Remember, only if the approved SDHC logo appears on the card or package, the product is compliant with SDA 2.00 specifications.

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