## 5 Discussion  
One of the main limitations of EEG monitoring is the recording electrode; its principle of operation and application to the scalp has changed very little since EEG's first introduction as a clinical tool. With the evolution of amplifiers and data acquisition systems,  
Figure 11: Concentration level of an experienced driver and a less experienced drivers. Figure 12: Concentration level of people performing simple manual tasks. modern-day EEG systems now have the capability to record for multiple hours or even days with little intervention [20]. The research carried out has confirmed that it is possible to detect the level of concentration of machine and vehicle operators during their work. As the working characteristics of a mining machine operator are very different from those of a car driver, it will be necessary to carry out specific studies in order to propose a dedicated system concept designed for this group of people. It is assumed that, for reasons of user comfort, the measuring elements should not interfere with the work. It was therefore decided to place them inside the operator's helmet, as shown in Figure 13.  
The electronic module shall be mounted in the upper part of the miner's helmet, and the measuring probe will be guided to two points on the operator's forehead, which are the reference points for measuring the EEG signals. A suitable housing shall be used as the EEG signal inputs need to be protected against electromagnetic pulses (EMP) in accordance with the IEC 61000-4-2 recommendation [21]. The system model was built on the basis of a freely available market solution, Mind-Wave Mobile, which analyses the acquired EEG signal and performs its evaluation by generating a focus level signal. In the proposed 3D prototype model of the system, it will be necessary to develop a hardware solution and algorithms that will allow appropriate analysis of the acquired EEG signal. It will also be necessary to verify the proposed placement of the measurement electrodes. The readable field strength of the electromagnetic field emitted by the operator's brain ranges from a few to tens of microvolts (\(\upmu\)V). It was therefore necessary to use a signal amplification circuit. After amplification, the signal was filtered in order to extract specific frequencies. It is planned to use a band-pass filter to extract the frequencies of alpha waves (8-13 Hz) and theta waves (4-8 Hz) from the amplified EEG signal [22; 23; 24]. These waves carry information about the level of focus and meditation. In our prototype solution, we intend to use a single-electrode solution for EEG signal measurement. The electrode will be placed on the forehead of the operator. There is a possibility of interfering with the measurement in a single-electrode system. However, this matter was verified during the carried out tests. In addition, the location indicated for the measurement of alpha waves was the occipital region, while theta waves were found in the temporal region. However, these waves were also present in the frontal region, as confirmed by this study. However, if the results of the prototype tests under real-time operating conditions will indicate too high level of interference, additional measuring electrodes will be used. Figure 13: Prototype of a device for measuring EEG signals for machine operators. The operator's focus level data will be delivered in a wireless manner to the main server in an underground mine environment and then transmitted on the surface to the supervisory visualization system, shown in Figures 14 and 15. The device mounted inside a helmet will be one of the nodes in a wireless network with a mesh topology, where the routing process will be performed by algorithms based on swarm intelligence (SI). These algorithms are characterized by the fact that, regardless of the number of variables in the solution space, they adapt to the constraints and help to solve the optimization problem.