Microstrip filters and methods of operation are described. The set is formed with a venting mechanism that permits an outflow of air, while blocking an outflow of blood or other fluids. The control unit may perform the luminosity control of the backlight according to a residual capacity of the electricity storing unit. Another embodiment provides for the determination of an interference level I using power level measurements taken during the guard and ramp fields. The alumina fibers are also capable of filtering sub-micron inorganic and metallic particles to produce ultra pure water.