Abstract: This paper introduces a microcontroller-based test system for railway frequency-shift signals based on the width measurement method. The system utilizes an 8052 timer T2 to capture the zero point of the frequency-shift signal (i.e., the point where the phase angle of the frequency-shift signal is θ), and then calculates a series of periods of the frequency-shift signal (i.e., width measurement, measuring the period of the frequency-shift signal). By analyzing these periods, the upper sideband, lower sideband, center frequency, and low frequency of the frequency-shift signal can be obtained. Keywords: Frequency-shift signal; width measurement method; zero-point capture Abstract: The system that uses the single-chip computer to detect the frequency of the frequency-shift wave with the method of measuring wave width is introduced. This system uses the time of the single-chip computer to capture the zero point of the signal (or the phase angle is ), then finds out the period of the signal, and works out the upper frequency, the lower frequency, the middle frequency and the low frequency. Key words: Frequency-shift wave; measuring width; capturing the zero point of the signal 1 Introduction With the development of railway speed increase, multi-information frequency-shift automatic block system has been widely used in railway section automatic train operation control system. Railway frequency-shift signal is a frequency modulation signal. Usually, the (550-850) Hz frequency is selected as the center frequency and the (7-30) Hz frequency is selected as the low frequency modulation frequency. Each frequency-shift signal represents a certain speed information and directly controls the train running speed. Therefore, real-time detection of frequency-shift signal and timely detection of anti-interference source are of great significance to ensuring railway operation safety. This paper presents a frequency signal detection system based on a microcontroller, using the width measurement method in time-domain detection. The system utilizes the falling edge capture function of Timer T2 on an 8052 microcontroller to measure a series of periods of the frequency-shifted signal. These periods are then analyzed to derive the upper sideband, lower sideband, center frequency, and low frequency of the frequency-shifted signal. For more details, please click: Application of Microcontroller in Frequency Detection of Frequency-Shifted Signals.