An electrical signal filter in which circuit provided with filter circuits are inserted into a cylinder-shaped shield case, has a first cavity portion having an inner case. The side of one end of the inner case has the circuit boards inserted, and the side of the other end thereof is provided with one...http://www.google.com.au/patents/US5150087?utm_source=gb-gplus-sharePatent US5150087 - Electrical signal filter and method for manufacture of electrical signal filter internal circuit board
