PURPOSE: To reduce a charge for using a line by comparing the picture signal of an object obtained in a normal state and another picture signal currently obtained from a telecamera and transmitting the picture signal only when the change of the object is detected.

CONSTITUTION: The picture signal in the normal state of the object is written to a picture signal memory 22. Next, when an operation part 24 is operated, and the picture signal is made into a state to be written to a buffer memory 23, while no control signal is outputted from a comparing part 25, and the picture no control signal is never transmitted using a line 3 when no change occurs in the object, the control signal is outputted from a comparing part 25, and a transmitting part 26 reads out the picture signal from the buffer memory 23 and transmits the read out picture signal when even a slight change occurs in the picture signal of the object because of the invasion of an invader, etc. Thus, the line 3 can be used only in necessary time, and the charge for using the line can be reduced.