## 4 Measuring the Electromagnetic Field from a Smartphone  
These measurements show the presence of electromagnetic fields generated by different models of GSM devices in different operating modes. Depending on where the measurements are made--outdoors or indoors, the results differ. The obtained values additionally vary depending on how far the smartphone is from the measuring equipment or from the distance to the base station, as well as what additional radio sources are nearby. For this purpose, experimental measurements were performed in which the GSM device was positioned at distances of 1 and 10 cm from the smartphone. The average measurement results are shown in Table 2. Measurements were obtained with Gigahertz HFE35C.  
The data in Table 2 show that, in search and talk mode, the emission levels are many times higher than in passive mode. When ringing, the signal level is high for the first 20 s, and then decreases significantly. Depending on the location of the smartphone, the signal levels are different, and when indoors, the signal level may be above the normal values. The measurements were performed both indoors and in underground rooms, where the signal source from the base station was extremely weak, and, in order to achieve successful communication, the radiation level of the GSM device was at the maximum value to compensate for attenuation and to not let the conversation fail.  
Studies have shown that the level of the electromagnetic field in urban conditions is many times higher than in rural areas. This confirms the assumption that the presence of different types of electrical devices and transmitters will lead to a significant increase in the background electromagnetic field. With the development of technology, this problem will  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variance** & **Sum of Squares (SS)** & \(K\) & **Mean Square (MS)** & **F-Ratio** \\ \hline Between groups & \(SS_{b}=\sum_{j=1}^{k}n_{j}(\bar{x}j-\bar{x})^{2}\) & \(k-1\) & \(MS_{b}=\frac{SS_{b}}{k-1}\) & \(F=\frac{MS_{b}}{MK_{\omega}}\) \\ Within groups & \(SS_{w}=\sum_{j=1}^{k}\sum_{i=1}^{n_{j}}(\bar{x}ij-\bar{x}j)^{2}\) & \(n-k\) & \(MS_{w}=\frac{SS_{w}}{n-k}\) & \\ Total & \(SS_{T}=\sum_{j=1}^{k}\sum_{i=1}^{n_{j}}(x_{ij}-\bar{x})^{2}\) & \(n-1\) & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: One-way ANOVA [16].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**GSM Operating Mode** & **Distance between GSM and HFE35C [\(\mu\) W/m\({}^{2}\)]** \\  & **1 cm** & **10 cm** \\ \hline \multicolumn{3}{c}{**Outdoor**} \\ \hline Passive mode & 2 & 2 \\ Search mode & 520 & 150 \\ Conversation mode & 515 & 230 \\ \hline \multicolumn{3}{c}{**Indoor (Second floor of a building)**} \\ \hline Passive mode & 2 & 2 \\ Search mode & 640 & 220 \\ Conversation mode & 1550 & 530 \\ \hline \multicolumn{3}{c}{**Indoor (underground floor)**} \\ \hline Passive mode & 2 & 2 \\ Search mode & 860 & 310 \\ Conversation mode & Over 2000 & 1450 \\ \hline \hline \end{tabular}
\end{table}
Table 2: EMF values generated by a GSM device.  
deepen and become more relevant. One of the most serious generators of electromagnetic fields is the smartphone. The level of the electromagnetic field generated by these strongly depends on the mode of operation and the environment in which the phone is located. In some cases, the levels of electromagnetic fields exceed the regulated permissible levels. The proximity of these devices to the human head requires in-depth study of the influence of electromagnetic fields on the possible effects on the human body.