| 摘要 |
<p>On the first part (co) of a cover an armature (ar) is mounted, having a wheel (wh) clamped in a freely turnable manner, which is rolling across the second part (wa) of the cover when the latter is being opened. The wheel is fitted with a brake (b) with two different brake torques when the wheel is turning in the one and the other sense, and is connected by a shaft (sh), centred in its rotation axis, to a rotating capacitor's plate which can be turned for an unlimited angle. The capacitor determines the resulting capacity within the oscillation circuit the cover is equipped with. The occurrence of a relative change of the oscillation circuit frequency (fn+1 - fn)/fn, different from zero, during two consecutive frequency checks is preferentially automatically communicated to the supervision site. In order to detect any opening, even in the absence of the supply voltage, the cover according to the invention is equipped with standard components in a simple and reliable manner.</p> |
