US Patent 10007813 Card reader with passive ID circuit

A method of transmitting information to a mobile device includes providing a card reader is provided with a read head, a slot for swiping a magnetic stripe of a card and device electronics that includes an analog front-end and a microcontroller. The analog to digital front end is coupled to a processing element in the microcontroller. A raw magnetic head signal is received at the analog to digital front end. The raw magnetic head signal is converted into a processed digital signal that the microcontroller can interpret. An output jack output jack signal is delivered to the mobile device.