Magnetic field-based communication with an object is enhanced by generating a rotating AC magnetic field that effectively ensures magnetic field coupling with the magnetic field sensor of the object, irrespective of the orientation of the object. The first structure may be a generally elongated optical pipe adapted to receive light from at least one light source such as a light emitting diode. The valve seat is located closer to the outlet port than to the inlet port. The signal is received by base stations that then use the signal to locatetrack the signal emitter. An organic material is deposited into each of the plurality of gaps. The scaleable recovery process includes an end-of-log locating process for locating the end of the multiplexed log and each of the virtual logs with the multiplexed log.