The reference level for the relative attenuation arel of the TFS 208B is the maximum attenuation in the pass band. The maximum attenuation in the pass band is defined as the insertion loss ae. The nominal frequency fN is fixed at 208 MHz without any tolerance or limit. The values of relative attenuation arel are guaranteed for the whole operating temperature range. The frequency shift of the filter in the operating temperature range is included in the production tolerance scheme.