Vehicular communications 2500 feet underground

Abstract

An underground communications system has been installed in Bethlehem Mines Corporation's Grace Iron Mine. The system provides communications for trackless vehicles and roving personnel without the requirement for a dispatcher. UHF/VHF repeaters are combined with coaxial "leaky-feeder" and twin-lead transmission line to form an operational and emergency communication network not previously found in mine communication systems. Key functions are evacuation alarming, personnel paging and communications with maintenance personnel and the underground ambulance.