## 4 Test Images and Test Conditions  
The measures and criteria for determining the correct length lines \(d_{\Delta}\) of the reconstructed image presented in the previous chapter have been verified on the basis of the actual test results. The results of these tests are the registered revealing emission signals, the source of which were the graphic lines of the computer set and the display of the multifunction device. The test images used in the research and the view of the device display are shown in Figure 7. As test images, there were proposed text data (texts written with different fonts and in different character sizes) and photos showing different views. The variety of test images allowed for a detailed analysis of the proposed measures and criteria in the process of estimating the correct length line \(d_{\Delta}\) of the reconstructed image.  
Figure 7: Images displayed on a computer monitor (**a-c,e,f**) or multifunction device display (**d**), which are the source of revealing emissions: (**a**) a photo showing the road along the bushes, (**b**) a photo of the inside of an anechoic chamber, (**c**) three words “protection”, letter size 36, Arial font, (**d**) letter signs written with four fonts Safe Symmetric, Arial, Safe Asymmetric, Times New Roman, (**e**) a sentence written in Arial font of various sizes of letters, (**f**) display screen (Configuration menu) of the multifunction device.  
The tests of the revealing emission signals, which are the basis for the reconstruction of data in the form of images, for which the process of determining the correct length lines was carried out, were carried out in an anechoic chamber. The measuring test system is shown in Figure 8. The measurement system TEMPEST Test System DSI-1550A and the FSWT26 receiver from Rohde & Schwarz with a set of measurement antennas (a vertical active rod antenna (100 Hz up to 50 MHz), a biconical active antenna (20 MHz up to 200 MHz) and a dipole active antenna (200 MHz up to 1000 MHz)) were used in the tests. The PDA-1000 8-bit analog-to-digital converter card, manufactured by Signatec (PDA100 Scope Application software, version 1.19), was used to sample the revealing emission signals. The card offers a signal sampling rate of 1 GS/s, which may be reduced by using the card clock frequency division in the range from 2 to 1024.  
Initial (rough) line length estimation was performed in the Program Raster Generator for the given catalog operating parameters of the test computer monitor (for known parameters). If such parameters are not known-no access to the eavesdropped monitor or for the displays of multifunction devices-their rough estimation can be performed in accordance with the algorithm of the Chirp-Z transform or periodicity analysis of the recorded emission signal of revealing [34; 35; 52; 53]. As previously mentioned, this is the step of roughly determining the line length of the reconstructed image. In the first stage, the line length estimation is performed with accuracy to unity in the vicinity of \(\pm 10\) around the roughly determined d value of the line length. This means that for \(d_{1}=1087\), the estimation of the value of \(d_{\Delta}\) is carried out in the range from 1077 to 1097, in which the maximum (minimum) of the adopted measure may correspond to the value of 1089. Similarly, if the accuracy is increased to 0.1, the estimation is carried out in the range from 1088.0 to 1090.0 in steps of 0.1. Then, for the determined length \(d_{\Delta}\) with an accuracy of 0.1 (e.g., 1088.4), the estimation accuracy is increased to 0.01. Calculations are performed in the range from 1088.30 to 1088.50. Details of the line length estimation of the reconstructed image with an accuracy of up to 0.00001 are described in the form of the algorithm shown in Figure 9.  
Figure 8: The measuring system of revealing emission signals.