Research and development contract for coal mine communication system. Volume 2, Mine visits

"Eight coal mines were visited to determine their communications usage and requirements. Presently available equipment was surveyed and evaluated to determine its applicability to the needs of the mines. The requirements, as determined from surveys, and the capabilities, as determined from analysis and experiments, were summarized. Volume 2 details the eight mine visits, along with the conclusions reached following each visit and the final conclusions reached when the requirements of all mines visited were considered." - NIOSHTIC-2NIOSHTIC no. 10001393523-0 765829-00 12 7 MUSBM contract no. H023205