The present invention provides a communications network which is divided into a plurality of segments, with each segment comprising one or more routers and one or more communications links that connect the routers. The telephone call request omits a name of a calling party. The second substrate comprises a common electrode thereon, wherein the common electrode has second openings therein, and the second openings and the first openings are arranged in an overlying and cross-over relationship with respect to each other. The data control unit reads the serial data in the block constituting the write destination of the write data, before storing this serial data in the data storage unit, and updates the stored serial data by means of the write data. In some applications, the invention may be used to used to improve patency or fluid flow through a body lumen or cavity.