Patent US 5,478,992

When sheets are taken into a machine or discharged from the machine, characteristics of these sheets such as letters or symbols of these sheets are read by a sheet characteristics reading unit. A result of reading the characteristics is stored in a storage unit. When characteristics of a sheet are not able to be read at the time of accommodating sheets, this sheet is returned and only sheets of which characteristics have been able to be read are taken into the machine. Sheets of which characteristics are not able to be read at the time of discharging sheets are specified by a unit for specifying sheets of which characteristics can not be read. By this arrangement, each sheet in the machine is always managed.