When a history including printed information, a date, a user, and the like is stored, a search for stored information is allowed, and the history can be referred to if information has leaked, a large-capacity storage device is required to store all images in the storage device. In a receiving unit 170 of the first information processing unit 100, log information generated by a purchase processing module 153 is stored into the storage module 152 every time the contents key is decoded, and the log information is transmitted at predetermined timing to a key management center 30 through the transmission section 110. A transmitter is also included, which has a complementary hole therethrough. The additional information my include a user-configurable list of desired callers andor undesired callers. The computer system is configured to receive voice commands from a user to manage the stored list, including adding the caller ID information from a current or recent call to the list. Neutral piston assembly engages range control piston assembly responsive to pressurization of neutral chamber.