PURPOSE: To reduce the time when a print start instruction is given from a scanner to a printer till the printer starts printing.
CONSTITUTION: A scanner 1 sends a picture forming request signal(PREPR signal) to a printer 2 via a standby signal line Sg. The printer 2 sends a print request signal(PREQ signal: picture signal output request signal) to the scanner 1 via a request signal line Sh when each section for print-out is brought into the standby state by the received PREPR signal. Upon the receipt of the PREQ signal, the scanner 1 sends a print start synchronizing signal(PRINT signal: print start signal) to the printer 2 via a print signal line Si and sends a picture signal (VDAT7-0) thereto via a data line Se. The printer 2 receiving the PRINT signal and the picture signal starts immediately printing.