PURPOSE: To discriminate recording lines easily even if they cross or are superposed, by adding discrimination symbols corresponding to respective recording lines when plural recording lines approach one another within a certain interval.

CONSTITUTION: Signals inputted from an input terminal 10 are selected successively by a multiplexer 11 and are taken into a processing device 20 through an A/D converter 12 and an I/O port 13. When recording lines of respective channels approach one another within a certain value on the same line, the processing device 20 prints discrimination symbols corresponding to thses respective channels to recording lines.