Parkinson, Howard E.
Mine pager to public telephone interconnect system / by Howard E. Parkinson. - [Washington] : U.S. Dept. of the Interior, Bureau of Mines, [1974]. - 14 p. : ill. - Report of investigations ; 7976 . - United States. Bureau of Mines. Report of investigations ; 7976 . - Report of investigations (United States. Bureau of Mines) ; 7976 .
91055141
Telephone in mining.
Mine communications systems.
Mine pager to public telephone interconnect system / by Howard E. Parkinson. - [Washington] : U.S. Dept. of the Interior, Bureau of Mines, [1974]. - 14 p. : ill. - Report of investigations ; 7976 . - United States. Bureau of Mines. Report of investigations ; 7976 . - Report of investigations (United States. Bureau of Mines) ; 7976 .
91055141
Telephone in mining.
Mine communications systems.