The reference level for the relative attenuation arel of TFS 350C is the minimum of the pass band attenuation amin . This minimum is defined as the insertion loss ae . The nominal frequency fN is fixed at 350 MHz without any tolerance. The given values for the relative attenuation arel and the group delay ripple have to be reached 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.