| 摘要 |
A position or movement sensor responsive to movement of a mine cage (26) in a mineshaft comprises a leaky coaxial cable (12) extending along the path of the cage, and an oscillator (40) and associated circuitry (42, 44, 14) for forming an electromagnetic standing wave in the cable. The cage carries a resonator (28) which moves adjacent the cable, causing a cyclical change in the cable characteristics as seen from a detector probe (30) at the top end of the cable. Detection and counting circuitry (32) detects and indicates movement of the cage by reference to the standing wave pattern.
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