Abstract: An underground wireless transmission system including: a sensor for sensing the underground environment and producing a corresponding data value; a data value transmission unit for transmitting the data value to the surface, the transmission unit providing an encoded low frequency magnetic oscillating field, modulated with the data value; a surface receiver unit including a magnetic sensor for sensing the encoded low frequency magnetic oscillating field and demodulating the data value from the field; and a surface control unit connected to the surface receiver unit for collation of the data values from one or more surface control units.

Abstract: A housing for a mine marker that houses RFID electronics. The RFID electronics is surrounded by a resiliently deformable tube that fits inside the housing, which may be an impact resistant plastic. The housing is filled with a first strengthening material and the tube may be filled with a second strengthening material. There is an impedance mismatch (a change in properties between adjacent layers so that shock waves are deflected) at the boundary between adjacent materials, (casing and first strengthening material, first strengthening material and tube, tube and second strengthening material, or casing and tube if they abut) which inhibits shock propagation.

Abstract: A housing for a mine marker that houses RFID electronics. The RFID electronics is surrounded by a resiliently deformable tube that fits inside the housing, which may be an impact resistant plastic. The housing is filled with a first strengthening material and the tube may be filled with a second strengthening material. There is an impedance mismatch (a change in properties between adjacent layers so that shock waves are deflected) at the boundary between adjacent materials, (casing and first strengthening material, first strengthening material and tube, tube and second strengthening material, or casing and tube if they abut) which inhibits shock propagation.