A method and apparatus for maintaining a purged optical gap between a pellicle and a reticle in a photolithography system. A plurality of openings extends through the base and a plurality of flaps closes the openings. The method also includes temporarily storing the write data into a buffer memory, and at a delay time point, transmitting a response message to the host, the delay time point is set by adding a dummy delay time to a time point that the operation of writing the write data into the buffer memory is completed. An alternate embodiment of the invention comprises a chamber having portions that form a resonant cavity, a low frequency microphone placed within the resonant cavity, and a membrane that covers the resonant cavity. The terminal device may send a print instruction including print setting information indicating the print setting to the printer. The transmitter generates an electromagnetic carrier that varies in frequency throughout a channel interval, and modulates the carrier with an information signal during the channel interval, whereby the carrier is modulated both in frequency and in accordance with the information signal during the channel interval.