| 摘要 |
A device 20 for preventing the use of a key 22 is arranged for fitting about at least a portion of the key such that it cannot be inserted into a lock with which it is intended to be used. The device 20 has a locking arrangement by which it can be locked in position about the key. The locking arrangement requires separate apparatus to permit release of the device once locked in position about a key. The device can engage the key shank or (as shown) enclose the whole key. Magnetic or electromagnetic locking means can secure the device. Alternatively snap-latches can secure two parts 24, 26 of an enclosure together and release means can be enabled by effecting a temperature change. A transmission element can be frozen to become sufficiently rigid to transmit an opening force or bimetal elements can be used.
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