An image processing device for curbing memory expansion and reducing costs while securing programming freedom by a small programmable data processing unit. A multistage iterative signal decoder is provided that exploits the property that in a relatively simply decoding scheme such as mean square error or zero-forcing only a small portion of the total symbols are mis-detected. A change in the electric potential on the body surface generates an electric field that induces change in the electric potential of the sensing plate. The module also has an electric circuit in the case with circuit elements responsive to the Hall effect sensor to provide a first mode of operation in response to the first signal and a second mode of operation in response to the second signal.