Abstract: This invention discloses a magnetic stripe card reader/writer apparatus comprising a card reader/writer device and a basic interface circuit. The recording head of the card reader/writer device is mounted on the end of a sensor arm and is driven over the magnetic stripe in an arcuate path by a head drive motor. The card reader/writer device includes a unique card locking mechanism which allows insertion of the card in only one manner and locks the card in place before initiating the reading or writing operation of the device. The interface circuit controls the forward and reverse motion of the head drive motor, converts magnetic data previously recorded on the card into digital information and records digital information onto the magnetic stripe card in the form of magnetic data.