The D-Series interference filters use multiple combinations of inductance L and capacitor C to create low-pass filters that suppress high-frequency interference at the interface. They are characterized by a very positive attenuation. The filters are made of 10 A to 1000 A. They are stored in stainless steel boxes with connection to the terminals, on copper strips by means of cable lugs or the construction is designed as an extension lead with sockets. They are suitable for military and other special purposes where there is high attenuation. Filters meet the requirements of the NBU/NSA for the degree of secret.