A regulator included in a high voltage generator for supplying a high voltage to a semiconductor memory device is disclosed. The first scanning unit includes all the mechanisms necessary to permit sheet-fed scanning of documents. A sealing rib extends inwardly from the inner surface of the main closure and is adapted to form a seal with the end portion of the container. The etch process is discontinued based on an endpoint detection system. Additional methods are specified that facilitate a referencing according to requirements.