## 4 Conclusions  
In the presented work, the use of the Electric Cell-Substrate Impedance Measurement method to monitor the vital functions of cell cultures in the presence of an electromagnetic field was presented. A testing culture of mouse fibroblasts was carried out under standard conditions in the ECIS system with a timer-activated telephone device operating in the GSM900 system.  
The results obtained from monitoring electrical parameters during the cell culture clearly indicate that there is a slow increase in impedance and resistance and a decrease in capacitance during the execution of a phone call. After disconnection, the values of these parameters slowly return to their levels before the phone call. It is likely that the apparent effect of changes in the measured parameters is mainly due to the reaction of the ions contained in the medium, and it cannot be conclusively stated that any interference with cell culture is due to the presence of radio waves.  
Therefore, using this method to study the effect of electromagnetic fields on cell culture would require solving additional problems related to ion migration (separation of positive and negative ions) in the medium. In the experiment, an antenna was used, which was fixed to one side of the wells; this resulted in the creation of an inhomogeneous electromagnetic field. The solution to the problem of ion separation could be to generate a constant electromagnetic field covering the entire volume of the well, which would require the use of a spherical antenna around the well.  
The recorded changes in the measurements of electrical parameters indicate that conducting in vitro breeding near a mobile phone may interfere with the conduct of research. The conclusion of the experiment is the need to limit the presence of electromagnetic radiation sources in the GSM range during research on culture cells.  
The potential of the method used indicates the possibility of further development. However, one-sided mounting of the antenna should be avoided, as this will affect the ion separation of the medium. One way would be to use an antenna that emits a uniform field throughout the well. This would require designing an antenna mounted around the well. In addition, for more up-to-date solutions, tests should be carried out on the frequencies of electromagnetic waves used in the 5G standard.  
Conceptualization, A.K. and T.M.-M.; methodology, A.K. and M.P.-W.; software, A.W. and D.P.-Z.; investigation, P.A.M.; resources, P.A.M.; data curation, A.K. and A.W.; writing--original draft preparation, A.K. and A.W.; writing--review and editing, M.P.-W.; visualization, A.K.; supervision, T.M.-M. All authors have read and agreed to the published version of the manuscript. This research was funded by the Lublin University of Technology under Grant FD-20/EE-2/311.  
Not applicable.  
**Acknowledgments:** Thanks to the Chairman of the Scientific Discipline Council of Automatic Control, Electronics and Electrical Engineering of the Lublin University of Technology, [PERSON], for financing the costs related to the publication of this work.  
**Conflicts of Interest:** The authors declare no conflict of interest.