| 摘要 |
A portable alarm particularly useful for protecting works of art in art galleries and museums is a self-contained alarm system in a display base member. The alarm is energized in response to the operation of either of two switches, in turn activated by spring biased plungers normally biased to extend out of the bottom and top surfaces, respectively, of the base member. When the base member is placed on a support such as a table, one of the switches is deactivated. When a work of art is placed on the top of the base member, the other switch plunger is depressed and its associated switch is deactivated. The alarm then is enabled for operation by a key operated switch connected in series circuit with the alarm and a silicon controlled rectifier (SCR). Removal of the art object from the top of the portable alarm base member or removal of the base member with the object placed on it, permits either one or the other of the plungers to be biased to the protruding position out of the surface into which it is normally depressed when the alarm is placed in its "set" position. This causes the alarm to be energized, alerting personnel to the fact that someone has tampered with it or with the object placed on top of it.
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