To reduce the transmission time of an entire information quantity in the case of normal transmission and to decrease a time delay until transmission on the occurrence of an interruption request.

In the case that the data transmitter transmits a process input signal of a control station to a station to be controlled and an interruption cause takes place in the process input signal, the data transmitter transmits its interruption signal to the station to be controlled with priority. The data transmitter is provided with a transmission text edit means 22 that edits the process signal into a transmission text with a prescribed text size when no interruption cause takes place and edits the interruption signal to a transmission text to the station to be controlled on the occurrence of an interruption cause and edits the process signal into a transmission text with a text size smaller than the prescribed text size for a prescribed period.