A read sensor of a magnetic head includes a sensor stack structure formed in a central region; hard bias layers formed in side regions adjacent the central region; and lead layers formed over the hard bias layers in the side regions. A connection between the source station and a server for the destination station is established. The power demand transition data is stored in a power database, and the power demand prediction data is stored in a prediction data storing unit. The multicarrier transmitter and receiver also uses a second polyphase filter having real coefficients which are selected as the real coefficients of the first filter with the sign of each odd-numbered real coefficient inverted. Hermetic seal can be attained for example using anodic bonding of a glass lid or using metal soldering.