Train safety is secured by the signalling system. The signal is transmitted to the train via rail track circuit. This transmission system is influenced by the train traction current in the rail. The track circuit transmission system of Shinkansen, the high speed train which operates at 275 km/h normally and at a maximum recorded speed of 440 km/h, adopts an SSB signal, which is synchronized with the power supply frequency, to avoid the influence of harmonic waves. This system has operated over 33 years without a fatal accident. Nevertheless the environment of the track circuit had become worse. The Central Japan Railway have undertaken basic experiments of a narrow band SS (spread spectrum) system which can endure a heavy noise environment. The experiments have been successful, and the theory and results are described.
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机译：信号系统确保了火车的安全。信号通过轨道电路传输到火车。该传输系统受铁轨中火车牵引电流的影响。高速列车新干线的轨道电路传输系统通常以275 km / h的速度运行，最大记录速度为440 km / h，它采用与电源频率同步的SSB信号，以避免产生影响谐波。该系统已经运行了33年，没有发生致命事故。然而，跟踪电路的环境变得更糟。日本中部铁路已经进行了可承受重噪声环境的窄带SS（扩频）系统的基础实验。实验已经成功，并描述了理论和结果。
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