Techniques, systems and methods for designing, implementing, and operating model predictive controllers that can deliver perfect tracking of set points and that can reject the effect of disturbances when steady-state operation is reached are disclosed. First and second electrodes 21 and 5 are provided in a chamber so as to face each other. The curved portions have an axis of curvature being perpendicular to the surface of the diaphragm layer at the location of the curved diaphragm portions. A plurality of cutting portions extend outwardly from the imaginary polygon and are equal in number to the number of side walls thereof. The recipient in the other carrier’s network may reply back to the ICSP’s sender using only the subscriber’s directory number.