Results 191 - 200 of 235

• Control and Monitoring Via Medium Frequency Techniques and Existing Mine Conductors
  7/1/1985 - Peer reviewed journal articles
  Medium frequency (MF) techniques have been successfully applied to the problem of radio voice communications in both coal and metal and nonmetal mines. MF techniques can also be applied to the areas of in-mine control and monitoring. Preliminary work in...
• A Medium Frequency Wireless Communication System for Underground Mines
  9/1/1984 - Contract reports, Open File Reports
  This report deals with information regarding a new Medium Frequency (MF) Wireless Communication System for underground mines. This new telecommunication system works on low loss electromagnetic wave propagation modes which allow it to provide quality ra...
• Electromagnetic Detection of Trapped Miners
  2/1/1984 - Peer reviewed journal articles
  The Bureau of Mines has conducted field studies in coal mines throughout the United States to determine the effectiveness of electromagnetic techniques in locating miners trapped underground following a mine accident.
• Underground Mine Communications, Control and Monitoring
  1/1/1984 - Information Circulars
  Since 1969, the Bureau of Mines has sponsored numerous programs aimed at improving methods of underground communication. This manual brings together relevant data from all previous reports, studies, and other sources, and presents these data in such a w...
• Field Test of a Post-Disaster Communication System
  12/1/1983 - Contract reports, Open File Reports
  A new postdisaster communication and location system using through-the-earth electromagnetic wave propagation was tested at the Bureau of Mines Lake Lynn Experimental Mine. This describes the testing process and findings.
• Development of a Phase Difference of Arrival Technique for Location of Trapped Miners
  9/1/1983 - Open File Reports
  Current technologies for locating trapped miners from the surface are either simple direction finders or time difference pulse systems that have accuracy limitations. Developing technologies using full-vector field measurements at several receiving poin...
• A Medium Frequency Wireless Communication System For Underground Mines
  1/1/1983 - Contract reports
  An underground medium frequency radio communications system has been developed and demonstrated in both coal and metal/non metal mines. The principal advantage of the system are its low cost, ease of installation and the ability to provide radio communi...
• Theoretical Noise and Propagation Models for Through-the-earth Communication
  9/1/1982 - Contract reports
  A survey of the literature on extremely low-frequency and very low- frequency atmospheric noise was made.
• A Multiplexed Phone System for Small Mines
  7/1/1982 - Conference papers
  A new phone system was developed that provides eight full duplex communications channels over a single twisted shielded phone line, with no central switching station or line amplifiers. This system greatly simplifies installation and maintenance over th...
• Evaluation of the Black River Mine Telecommunication System
  2/1/1982 - Contract reports
  An evaluation was made of one of several improved underground communication systems sponsored by the U.S. Bureau of Mines. The system was installed in a typical metal-nonmetal, room-and-pillar mine and utilized ultrahigh frequency repeaters connected to...