U.S. Patent No. 3,319,175 - 05/09/1967 - N.A.S.A. for Kramer, Manuel
Comments Concerning the Patent Gerald Stanley 03/03/2003: "Class-H amp. The best that many can offer for high-tech is completely articulated in this 1964 filed NASA patent by Manuel Kramer. The design is fully developed for N-level control."