PURPOSE: To transmit a still picture and a voice by means of a single telephone circuit and to simultaneously reproduce them by reading the voice data of a voice memory after the completion of a still picture transmission, transmitting them at high speed, and alternately repeating the transmission of the still picture data and voice data.

CONSTITUTION: The still picture data and the voice data are alternately sent from terminal facilities 12 to a supervising center 10, and in the supervising center 10, during the reproduction of the still picture data, the voice data received immediately before the still picture data is reproduced is reproduced simultaneously with the still picture reproduction over a time corresponding to an actual recording time. The voice is delayed by a time corresponding to that obtained by adding a transmission time T2 of the voice data to a transmission time T1 of the still picture data by one page, whereas, since voice monitor does not make conversations into an object, and listens to the abnormal sound in a warning zone, a time lag is not a serious problem. Thus the still picture data and the voice data are transmitted through a single telephone circuit, and the reception side can simultaneously reproduce them.