An embodiment of the present invention includes the use of a single connection to measure the resonance frequency of main cells or side cells of a resonant structure, such as a linear accelerator cavity structure. The method includes receiving at least one encryption key from the SP, receiving a broadcast control message comprising a second encryption key, and decrypting the broadcast control message with the at least one encryption key to obtain the second encryption key. Preferably, the first natural frequency is substantially higher than any ordinary operating frequency or driving frequency of the appliance. The first opening has a cross-section with a diameter, and each of the first openings is capable of emitting a pressurized gas which surrounds one of the extruded molten filaments. The IMC also preferably includes microcode for specific decompression of particular data formats such as digital video and digital audio. In this way, a uniform temperature in the fuel cells can be assured to that the power density can be increased while avoiding hot spots andor the service life can be increased.