The SparkFun SEN-08634 is a heavy duty, low coercitivity, three track magnetic card writer and reader.

This unit takes power from an available PS2 port (includes a pass through connector so you can still use a mouse or keyboard) and passes information through the RS232 serial port.

Please note: This writer works with low coercitivity cards only.

Datasheet om Magnetic Card reader/writer

Command Set