磁気誘導コンパス
US granted 1047157, Bliss, Donald M, "Device for Determining Direction", issued 1912-12-17, assigned to Henschel, Charles J
US granted 1840911, N. Minorsky, "Induction compass", published 1932-01-12, assigned to N. Minorsky
US granted 2434324, Lehde, Henry, "Earth inductor compass", issued 1948-01-13, assigned to Control Instrument Company Inc.
GB granted 314786, Vion, Eugene, "Improvements in electro-magnetic apparatus for the observation and correction of travel of aerial and marine craft", issued 1929-12-23