The reference level for the relative attenuation arel of the TFS420H is the minimum of the pass band attenuation amin. The minimum of the pass band attenuation amin is defined as the insertion loss ae. The centre frequency fc is the arithmetic mean value of the upper and lower frequencies at the 3 dB filter attenuation level relative to the insertion loss ae. The nominal frequency fN is fixed at 420 MHz without any tolerance. The given values for the relative attenuation arel have to be achieved at the frequencies given below even if the centre frequency fc is shifted due to the temperature coefficient of frequency TCf in the operating temperature range and due to a production tolerance for the centre frequency fc.