| 摘要 |
A vital wheel detector for railways injects an oscillating electrical current into a short rail segment and produces a monitor signal in response the magnetic field around the rail. A high Q pickup coil is employed which, when a car wheel is present on the rail segment, sharply decreases in Q and significantly reduces the level of the monitor signal. Any failure of the detector apparatus is in a safe mode, as a loss of rail current results in a loss of the monitor signal whether through an electrical or a mechanical failure. Also, internal mechanical or electrical failures either interrupt the current to the rail or interrupt transmission of the monitor signal to the processing logic.
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