A method of restricting Address Resolution Protocol table updates to updates originating from authorized subsystems is disclosed. The operational amplifier includes an inverting input terminal connected to the input resistor, a non-inverting input terminal to which a reference common voltage is applied and an output terminal. Due to the small separation between the pole tips and the media layer, the magnetic field generated by the transducer and felt by the media has a larger perpendicular than longitudinal component, favoring perpendicular recording over longitudinal recording. A liquid crystal layer is sealed between the two substrates.