To increase safety in the event of access to a total system 1, in particular a medical system, with a field of high magnetic field intensity 3.1, an optical signal is provided in the form of a luminescent display field 24 graphically reproducing the field of high magnetic field intensity 3.1; according to one embodiment of the invention a representation of the luminescent display field 24 is provided by means of photodiodes 31 arranged on the floor and reproducing the field line pattern and/or the different field intensities by means of corresponding different colors.