Hartley 1928
Ralph V.L. Hartley of South Orange, N.J. assigned rights to Bell Telephone Labs., N.Y. "Acoustic Device" Filed: June 6, 1928 U.S. Patent 1,762,981 Granted: June 10, 1930

Hartley 1928

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Filed: June 6, 1928
U.S. Patent 1,762,981
Granted: June 10, 1930

Ralph V.L. Hartley of South Orange, N.J. assigned rights to Bell Telephone Labs., N.Y.
"Acoustic Device"

Referenced by Walker and Williamson in U.S. Pats. 3,008,013 & 3,008,014