| 摘要 |
AEST1RACT OF THE II~1VENTION An apparatus for detecting speed sensor failure in an overspeed protection device is disclosed, The apparatus comprises a plurality of tachometers having outputs for indicating the speed of rotation of a machine relative to plural setpoints. If the comparison indicates that certain conditions exist, then a sensor failure is indicated. The apparatus may also be employed to detect a failure of, or loss of power to or within, one of the tachometers.
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