| 摘要 |
<p>There is provided an alarm, which includes a mounting base, and means for securing the mounting base to an item whose movement is to be signalled by the alarm. A magnetic reed switch constitutes a first element, and a magnet constitutes a second element. One of these elements is mounted on a pivotal member capable of pivoting with respect to the mounting base, while the other of the elements is capable of retaining a given position with respect to the mounting base. Means is provided for adjusting the relative distance from the pivot location for the pivotal member to the location of said other of said elements, between a separated position in which the reed switch is unaffected by the magnet regardless of pivotal movement of the pivotal member, and a juxtaposed position in which the reed switch is a) unaffected by the magnet when the pivotal member hangs initially in an equilibrium position, b) closed by the magnet when the pivotal member swings through a given displacement from said equilibrium position, and c) remains closed after the pivotal member swings back to said equilibrium position, an electrically-powered signal-creating device, and an electrical circuit by which power from a power source is supplied by way of said reed switch to said signal-creating device.</p> |
