US Patent 7246752 Magnetic stripe card with dynamic numbers

A magnetic stripe card includes a magnetic stripe, a plurality of magnetic write heads, and data circuitry. The magnetic stripe stores magnetic fields indicative of a dynamic number. The plurality of magnetic write heads located under the magnetic stripe generates the magnetic fields to write bits of the dynamic number onto the magnetic stripe. The data circuitry generates the dynamic number and sequentially provides the bits of the dynamic number to the plurality of the magnetic write heads.