PURPOSE: To attain the improvement of performance close to twice by preparing a buffer memory to a CFC so as to allow the CFC to receive a document data of the next page from a computer while the CFC outputs a document to an FAX.

CONSTITUTION: The 1st page of the document data is transmitted from a CCP to the CFC. When dot patterning is finished, the CFC informs a +RSP to the computer. An output is started to the FAX while the content of a bit map memory is subject to compression coding at this point of time. When the computer receives the +RSP, the computer supplies a command of MPS to the CFC with the presence of the next page output. The CFC returns the +RSP to the MPS command without awaiting an FAX output and supplies a data request of the next page to the computer. When the 2nd page of document data is transmitted from the computer to the CFC, the CFC stores it in the internal buffer memory section. When the FAX output of a picture data of the 1st page is finished, the CFC transmits the MPS signal to the FAX.