A three-phase 48-pulse rectifier transformer includes two 24-pulse rectifier transformers phase-shifted through valve-side output windings. Information that a computer can use to authenticate a portable device and establish a trusted relationship prior to creating an association with the portable device is created and stored in a data store that is accessible by a plurality of computers and is associated with a user of the portable device. The scissor piece includes a first edge, and the holder includes a second edge that intersects and contacts the first edge. An inserting pin seat is installed in the sliding groove, and an elastic element is installed between the inserting pin seat and the closed end of the sliding groove.