Title:
Earth borehole investigation-signaling system
United States Patent 2759143
Inventors:
Arps, Jan J.
Application Number:
US44330854A
Publication Date:
08/14/1956
Filing Date:
07/14/1954
Assignee:
Arps, Jan J.
Primary Class:
Other Classes:
73/152.43, 73/152.53, 137/78.5, 307/132R, 324/356, 367/83
International Classes:
E21B47/18; G01V3/34
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