无码日韩爆乳少妇无码,中国又大又粗又黄,操逼一区二区,95资源国产在线,国产粗大劲爆内射,国产又粗又黄又大的视频,在线国产无码,亚洲丰满熟妇浓毛大隂户,av无码人妻美乳免费,国产又粗又猛又大爽又黄的

Coal mine gasexplosion underground,roof caving,flooding and otheraccidents have occurred from time to time.How toadvance goodprotection,after theloss to a minimum,how to achieve a betterrescue work,causes the ground totimely understand theundergroundscene of the accident,the implementation of theminerescue workcommand,emergency communicationsystem of coal minesecurity monitoringcan play a crucial role.The traditionalcoal minecommunication systemequipmenthas been using afixedexplosion-prooftelephone,its coverageis small,only callin the fixed-point,anddoes not have mobility,which makesan emergencydispatch commandcould not be completedin the first time,the mainresponsible person can not berushed to the scene to understandanddeal with the emergencyin the firsttime.However,the mine roadwayis a nonfree spaceradio wavesis fundamentalconstraintsin the transmissionof underground laneway,over the yearshas carried on the positive explorationand research of manydomestic and foreign experts and scholarsin this field.This paperuses thelong wave communicationprinciple inunderground mine mobile communicationsystem iswidely used.