Abstract: An assembly formed by an electronic circuit in which a microprocessor is included that emits a signal from which additional signals are generated by a frequency synthesizer. These signals are applied to coils which form the emitting antenna, after being filtered and amplified. From these signals, the sample signal is generated and is picked up by other receiving antennas. After being amplified and filtered and all the distortion elements removed, the picked up signals are applied to proper frequency filters to obtain at the output signals having amplitudes proportional to those generated in the sample.