A method, system, and medium are provided for authenticating a visual voicemail client to a visual voicemail server. The light-absorbing coating comprises stabilized pigments which are incorporated in a sol-gel matrix. At least one of the flat and corrugated filter medium webs is a composite filter medium web of at least two components, wherein at least one component is a synthetic material and one component is a non-synthetic material. Additionally, penetrating radiation transmitted through the inspected object may be combined with scatter information. DC resistance of a common mode filter is equal to or higher than 0.