A communication provider which provides wireless access to a packetized data network, such as the Internet. For low data rates, the RF amplifier is controlled so as to allow significant output signal distortion, at the same time operating within a region of increased efficiency of the RF power amplifier. A length of the first and second conveyance paths is shorter than a length of a maximum recording medium of the image forming apparatus. After masking the silicon dielectric layer, at least one channel is etched in the photoresist layer and the silicon dielectric layer. In addition, non-zero elements, which are newly produced by the Gaussian elimination of the first pivot, are added to the coefficient matrix. This can avoid the possible drawbacks due to sintering of two different materials in the prior art.