An oscillator circuit includes first and second oscillators arranged in a series configuration between a supply voltage node and a reference voltage node. The cooling chamber 3, 23 includes flow guides in the form of vanes 7, 8 or grooves 37 which act to create a coolant flow in a spiral direction. The write control circuit is operable to iteratively perform iteration of a write operation for the plurality of addresses corresponding to one page and iteration of a verify-read operation of the plurality of addresses after writing until verify-read check is passed with respect to every address involved. From the sensible representation in the sensible format, a clean copy of the sensible representation can be generated such that any inappropriate content present within the received data signal is not reproduced in the clean copy. The coupling portion is provided at a position corresponding to an antinode of a primary bending mode of the first and second piezoelectric element units being respectively fixed in both ends. The content display unit creates the content list information based on the storage state of contents in a cache for delivering a content to the user terminal.