To reduce the memory requirements of a printer, it is desirable to compress rendered data of a to-be-printed page. A front portion 2 of a document validator 1 may be arranged in inner chamber 10 through notch 5a of back wall 5 so that users can easily take out documents in a lump from a pocket 13 of the document rack for reuse of documents because pocket 13 may receive and retain documents dispensed from document validator 1 to prevent scatter and contamination of the discharged documents. may be produced in a stable manner with high yield and high selectivity under mild and simple reaction conditions. In order to avoid anomalies, the queue is never allowed to become empty by requiring the presence of at least a dummy node in the queue. Each electrode may protrude into or extend into an interior portion of the plasma generation chamber. The result is a clarified sound that gives to the listening participant a sense of where the speaking participant is positioned relative to the listening participant.