| 摘要 |
<p>The device has a mounting unit to mount one of legs (11, 12) in co-operation with a base (10), and another mounting unit (30-1) to mount another leg in rotation relative to the base around a rotation axle (21) located near one of ends (11-1, 12-1) of each leg. The latter leg is mounted to rotate so as to rotate between positions (P1-1, P1-2, P2-1, P2-2). A detection circuit delivers a threshold signal when distance between other ends (11-2, 12-2) of each leg reaches a minimal value. A sensor delivers an alarm signal based on the threshold signal.</p> |
