Magnetic communication system comprised of at least one underground transceiver unit and one surface transceiver unit having common transmit and receive antennae for two-way, wireless, through-the-earth communications using advanced signal processing and optimized antenna design for mine safety and other applications, namely, emergency underground communications and location detection of trapped miners

VALVE POSITION INDICATORS FOR INDICATING THE EXTENT TO WHICH A VALVE IS OPEN OR CLOSED AND PARTS THEREFOR

magnetic power transmission couplings

LIQUID LEVEL GAUGES FOR USE IN FUEL TANKS AND THE LIKE