The hardware and software used as components for two of the world's most common technologies for continuous ultrasonic nondestructive testing of rails, namely, the classical technology, which consists in pretuning, and the technology of using an adaptive threshold, are considered. As applied to the hardware, the influence of such characteristics as the dynamic range of data recording, as well as the sampling of signal amplitudes is shown. A comparison for both versions of the software is provided. The differences in the interface and functionality are shown. Differences in the algorithms for automated interpretation of ultrasound control data are presented: different approaches to displaying a B-scan (continuous data recording and registration of fragments of flaw patterns with signals that meet the criteria for automated analysis), the possibility and informative value of A-scan, etc. Based on the results of the hardware and software analysis, the capabilities of two of the world's most widely used technologies for non-destructive continuous ultrasonic testing of rails in the world were evaluated.