Radio communication systems for underground mines
Patent 4777652 Issued on October 11, 1988. Estimated Expiration Date: 
October 11, 2005. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
October 11, 2005. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2285083 3505615 3543262 3609247 3750020 3803366 Distribution network powerline carrier communication system High voltage signal coupler for a distribution network power line carrier communication system Patent #: 4142178 InventorApplicationNo. 06/402258 filed on 07/27/1982US Classes:455/3.03, Remote control of distribution455/14, With transmission line455/15, Two separate way transmission455/41.1, Near field (i.e., inductive or capacitive coupling)455/523Using radiating transmission lineExaminersPrimary: Masinick, Michael A.Attorney, Agent or FirmInternational ClassesH04B 3/54 (20060101)H04B 3/58 (20060101) H04B 5/00 (20060101) H01Q 1/27 (20060101) AbstractA radio communications system operational within the medium frequency range for underground mine communications, coupling MF carrier signals into existing conductive channels extending to within the mine and devices within the mine and coupled to the conductive channel for receiving the MF carrier signals and communicating with portable and mobile transceivers operational within the MF frequency range and in the common seam mode.Other References
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