Most card readers are highly portable and versatile in their ability to read more than one type of memory card. The most common types of memory cards are Secure Digital (SD), microSD, SDHC, microSDHC, CompactFlash (CF), Memory Stick (MS), MS Duo, Mini SD, and MMC. Before buying a reader, make sure it's compatible with the memory card you are using.


In the 1-to-many mode a user presents biometric data such as a fingerprint or retina scan and the reader then compares the live scan to all the templates stored in the memory. This method is preferred by most end-users, because it eliminates the need to carry ID cards or use PINs. On the other hand, this method is slower, because the reader may have to perform thousands of comparison operations until it finds the match. An important technical characteristic of a 1-to-many reader is the number of comparisons that can be performed in one second, which is considered the maximum time that users can wait at a door without noticing a delay. Currently most 1-to-many readers are capable of performing 2,000–3,000 matching operations per second.
External devices that can read a Personal identification number (PIN) or other information may also be connected to a keyboard (usually called "card readers with PIN pad"). This model works by supplying the integrated circuit on the smart card with electricity and communicating via protocols, thereby enabling the user to read and write to a fixed address on the card.

If you've maxed out the memory on your camera, action cam, or smartphone, then there's a good chance you've invested in a memory card. Just one catch -- your laptop might not have a compatible port to speak with your memory card. That's where a card reader comes in. These handy go-between devices transmit data between a memory card and your computer. Let's answer some common questions about memory card readers.


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The advantage of using barcode technology is that it is cheap and easy to generate the credential and it can easily be applied to cards or other items. However the same affordability and simplicity makes the technology susceptible to fraud, because fake barcodes can also be created cheaply and easily, for example by photocopying real ones. One attempt to reduce fraud is to print the barcode using carbon-based ink, and then cover the bar code with a dark red overlay. The barcode can then be read with an optical reader tuned to the infrared spectrum, but can not easily be copied by a copy machine. This does not address the ease with which barcode numbers can be generated from a computer using almost any printer.
In the 1-to-many mode a user presents biometric data such as a fingerprint or retina scan and the reader then compares the live scan to all the templates stored in the memory. This method is preferred by most end-users, because it eliminates the need to carry ID cards or use PINs. On the other hand, this method is slower, because the reader may have to perform thousands of comparison operations until it finds the match. An important technical characteristic of a 1-to-many reader is the number of comparisons that can be performed in one second, which is considered the maximum time that users can wait at a door without noticing a delay. Currently most 1-to-many readers are capable of performing 2,000–3,000 matching operations per second.
There are two types of smart cards: contact and contactless. Both have an embedded microprocessor and memory. The smart card differs from the proximity card in that the microchip in the proximity card has only one function: to provide the reader with the card's identification number. The processor on the smart card has an embedded operating system and can handle multiple applications such as a cash card, a pre-paid membership card, or an access control card.