## 2 Information Reproducing by Using a Real Analog-to-Digital Converter (ADC)  
The assessment of the safety of emissions of devices intended for processing graphic information requires the determination of the possibility of their reconstruction from the recorded signals of revealing emissions. For this purpose, the image rastering technique is used, which requires the determination of its geometrical dimensions (width, height), taking into account the conditions resulting from the applied method of recording and visualizing these signals (sampling). In physical devices, the timing signals used for imaging are produced with a finite accuracy; moreover, the recording devices have a finite number of available sampling frequencies. For this reason, the width of the image (line length) to be taken into account in the rastering process is not expressed as an integer. The accuracy of its determination, however, is important in the case of signals for which, due to low SNR values, obtaining a clear image requires the use of coherent summation techniques. In this case, obtaining the accuracy of determining the row length at the level of \(10^{-4}\) using the FFT method requires transform calculations to be performed on sets of samples with sizes of the order of TB, which results in a significant extension of the computation time (several dozen-several hundred seconds) and the need to use large RAM memory resources (representation 64-bit). The use of the simple Fourier transform to determine the raster parameters is therefore a computationally inefficient process. The determined amplitude spectrum will largely remain unused. A more useful solution is the use of the CZT transform, which makes it possible to determine the spectrum of the signal only in a given frequency sub-range, with the required accuracy determined using a much smaller number of samples. The simulation tests were carried out with the use of two work stations:  
* Computer with 8 GB of DDR3-1333 RAM, Intel Pentium Core2 Quad Q8300 processor running at 2.5 GHz. For such a hardware platform, in a 64-bit Windows environment, the maximum samples string length for FFT transform calculations was \(2^{28}\) (256 MS). * Computer equipped with 64 GB of DDR4-2666 RAM memory, Intel Pentium i9-10900X processor with a clock frequency of 3.7 GHz. For such a hardware platform, the maximum samples string length for FFT transform calculations was \(2^{31}\) (2 GS). The average computation times (for 10 repetitions) of a single transform of a given length are shown in Table 2. The limiting values of the transformation length require computer memory management, i.e., resource allocation for computations. Out of memory errors occur when the amount of RAM is too low. The tests were limited to signals obtained analytically from the Word editor window image, and the accuracy of determining the parameters of rastering of \(R_{H}\) line length and the number of \(L_{V}\) lines for the use of the FFT and CZT transforms were compared. In the case of recording the revealing emission signals with an ADC, a specific sampling rate may be used. For example, the PDA-1000 8-bit analog-to-digital converter card, manufactured by Signatec, offers a signal sampling rate equal 1 GS/s, which can be reduced by dividing the card's clock frequency in the range from 2 to 1024. Assuming the perfect execution of both the transducer card and the graphics card elements and assuming that the minimum sampling frequency should be at least equal to the \"pixel frequency\", for the previously selected monitor operating modes (Table 1) and the ADC card the values of the acquisition and screening parameters of the EU signals were obtained (Table 3).