PURPOSE: To improve operability at the time of input by reducing a conflict between a value inputted to a transmission destination and a value which is really transmitted when a numerical value is inputted by means of increasing/ decreasing it in terms of analog and it is transmitted through a communication line.

CONSTITUTION: While an up key or a down key is depressed, (S6), the value (n) of increase/decrease difference, which is previously set, is added to the numerical value which is transmitted previous time or it is subtracted at every having set period (S1) so as to generate (S2) transmission data. Only when the difference between a transmission data value and a return data value is within previously set limitter LT (S3), transmission data is transmission-processed (S4). Then, the transmitted data value and the received data value are screen-displayed.