Extremely Low Frequency Seismic Communicator
We have developed an underground transmitter and portable topside receiver that allow trapped miners to communicate topside. When activated, the transmitter continually transduces a signal into the ground as seismic energy. The receiver collects and processes the ground signal. The presence of a valid signal indicates survivors, and the frequency of the signal indicates their position. The system has been tested in the Natural Bridge Caverns and in 15 seconds can provide a strong signal through over 200' of rock.