In order to establish rapid diagnosing in TDX signaling service, it has developed a PCM signal acquisition (PCMA) system which can analyze status of signals sent from/received to a signaling equipment, providing the fully electronic switching system. The system has a function of acquirement PCM signal of the preferred channel from the subhighway (SHW), connecting a universal signal transceiver unit (USTU) and time switch unit (TSU), and then it classifies the type of signal such as R2MFC/DTMF/CCT/VOICE, and finally discriminates the digit. This paper analyze the signal status of the PCMA system using the quick Fourier transform (QFT) based the symmetric properties, and discusses the algorithm of signal analysis and discrimination. In the experimental results, it shows the improved performance to the PCMA and reduce memory waste and process the real-time.