Source data is stored in a source data storage unit and a comparing device compares source data with destination data stored in a destination data storage unit. A destination address compressing unit compresses destination address information, and other accounting parameters are output with some delay. An accumulating device accumulates information from the destination address compressing unit as an address. A source address compressing unit compresses or delays information from an accumulating unit, and then outputs information. A source address carrier compressing unit compresses or delays information from the source address compressing unit, and then outputs information. A destination address source address carrier re-compressing unit compresses or delays compressed information from the source address carrier compressing unit, and then outputs information. A period abnormality detecting circuit in an accounting unit validates transfer data and prevents a wrong accounting process from being performed.