Results 211 - 220 of 235

• Medium-Frequency Propagation in Coal Mines
  8/1/1978 - Conference papers
  Medium-frequency (MF) waves can propagate in a coal seam, bounded above and below by conducting rock, in an approximate transverse electro-magnetic (TEM) transmission-line mode with the electric field vertical and the magnetic field horizontal. The theo...
• Underground Mine Communications
  1/1/1978 - Peer reviewed journal articles
  Extensive analysis of mine-communications systems has identified specific areas, in particular the excessive times required to locate key personnel underground, the inadequacy of existing phone systems in terms of capacity and privacy and the inability ...
• Electromagnetic Propagation in Low Coal Mines at Medium Frequencies
  1/1/1978 - Contract reports
  This report covers magnetic field strength measurements versus range and frequency in low to medium coal mines. Both quasi-conductor-free and conductor-proximity areas were investigated.
• Transmit Antennas for Portable VLF to MF Wireless Mine Communications
  9/1/1977 - Contract reports
  An investigation was made of the feasibility of developing compact transmit antennas and/or other means to efficiently couple VLF to MF band radio energy between portable wireless communication units in coal mines. The completely wireless communication ...
• Propagation of EM Signals in Underground Mines
  1/1/1977 - Conference papers
  This report is a comprehensive summary of the results of the propagation measurements program conducted for the Bureau of Mines.
• Underground Mine Communications (in Four Parts): 4. Section-to-Place Communications
  1/1/1977 - Information Circulars
  This Bureau of Mines report on underground mine communications addresses methods and equipment to meet the communication requirements of working sections and places of coal and metal-nonmetal mines. A review of the status of trapped miner detection is a...
• Underground Mine Communications (in Four Parts): 2. Paging Systems
  1/1/1977 - Information Circulars
  This Bureau of Mines report summarizes the research, development, and evaluation demonstrations conducted by the Bureau of Mines under the Coal Mine Health and Safety Act of 1969 to improve the means of notifying miners underground, who are away from th...
• U.S. Bureau of Mines New Developments in Mine Communications
  8/1/1976 - Conference papers
  A brief description is given of various Bureau of Mines research activities that have begun since July 1974 and are not being reported on by others at the Third West Virginia University (WW) Conference on Coal Mine Electrotechnology.
• Experience with an Integrated, Computer-Controlled Communications and Monitoring System at the Robena Mine
  8/1/1976 - Conference papers
  A whole mine, computer-controlled communication and monitoring system for both normal and emergency use is installed and operating in the U.S. Steel Robena Mine complex near Uniontown, Pa. Experience with the system is reviewed.
• Technical Services for Mine Communications Research: Task A, Task Order No. 1 - Applicability of State-Of-The-Art Voice Bandwidth Compression Techniques for Wireless Mine Communication
  7/1/1975 - Contract reports
  The applicability of voice bandwidth compression techniques to mine wireless communication systems is examined. Promise has been attached to such techniques because the lessened bandwidth gave hope for lessened received noise and hence increased operati...