SDHC (Secure Digital High Capacity) is a variant of Secure Digital offering higher capacity and speed, and was introduced in 2006 as version 2.0 of the SD specification.
Devices that support SDHC cards will still work with standard SD cards, but at slower speeds. However, older devices designed to work with standard SD cards (usually made before 2007) will not usually work with SDHC cards.
Standard SD cards are available up to 2 GB, whereas SDHC cards are able to offer up to 32 GB.
SDHC cards are rated for speed, with Class 2, 4, 6, and 10 available. The class number relates to the MB per second write speed, so a Class 10 card should offer a minimum of 10 MB/second. Some devices may specify a minimum card speed requirement.
Sources / Resources
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