United States Patent 1690279
Publication Date:
11/06/1928
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Primary Class:
Other Classes:
315/201, 324/133, 340/825.250, 324/128, 315/208, 340/332, 315/76, 369/70, 246/169S, 362/811, 315/250, 369/175, 236/69, 315/156, 362/276
International Classes:
G10L21/06; G10L21/00