Cardreader
Cheap DIY credit card reader project – “The reader mechanism shown was purchased from All Electronics for $1.50. The unit provides the magnetic head on a spring mechanism along with low level head signal amplifiers and data slicers. Three signal lines comming from the unit provide card presence, clock, and data. “ [via] – Link.

Related:
Magnetic Stripe Reader. Have you ever wondered what information is stored on the magnetic-striped cards in your wallet? Now you can find out. This project shows you how to make a magstripe reader for less than $40. Subscribers, log in and read it now, MAKE 01 – Page 106.