A magnetic head is composed to diminish disordered writing bits of a recording layer or reading noise caused by a magnetic field generated from an under layer without decreasing a writing magnetic field strength of the magnetic head. Evaluated parameters such as a CRC error rate of an ATIP signal, an FMDT jitter amount and a phase error between an ATIP synchronization signal and a frame synchronization signal of writing data are evaluated based on a range of set values. The example adjustable electrode also includes a logic configured to selectively control which of the two or more contacts deliver HFAC to the nerve to control whether the nerve electrode is in a first configuration or in a second configuration. The first locking member is pivotably mounted to the side wall of the bracket.