| 摘要 |
The indicator has an impact sensor (16) fixed to its casing for detecting when an armature (20) strikes a stop (25,26) limiting its movement. The sensor is a piezoelectric device. Several such indicators can be combined into a display. The indicator is tested by ascribing the output from the impact sensor to the activity of an electromagnet i.e. by detecting whether an armature has in fact moved as a result of an electrical excitation at an electromagnet.
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