In varying embodiments, the present invention incorporates a combination of structures suitable for providing a lightweight and portable projection surface. The invention allows to protect the anonymity of honest users and to revoke anonymity only in case of cheat for protocols based on a tree structure without using a trusted third party. Each terminal includes a contact portion for electrically connecting with an electronic card and a mounting portion for electrically connecting with the printed circuit board. The controller is further operable to energize the second write element to write a second magnetic servo pattern at least partially overlapping the first pattern, wherein the relative position of the second pattern is adjusted in response to the position signal.