The Parallax RFID Reader Module is a 125 KHz RFID reader, with a USB connection.
RFID can be kinda handy. Want to start your own library? Count how many times the kids go to the bathroom? You'll need an RFID reader for that..
The Parallax RFID Reader Module USB is a low-cost solution to read passive RFID transponder tags. Unlike their other RFID reader, this one is USB interfaced. Just jack it into your PC, and you're reading how many times Junior borrows your copy of MAKE magazine.
Note: a USB A to Mini-B cable is required. You'll also need RFID tags too!
There are a variety of transponder tags that come in different packages. Each tag has a specific range that is within 10% of the given distance for each type of tag due to environmental conditions and RFID modules.