| 摘要 |
A device adapted to rest on the top of a person's head for indicating head movement from a predetermined position includes a box-like member supporting an indicator assembly which includes a part spherical support plate nested within a part spherical wall of the member and being capable of multi-directional shifting relative thereto. The assembly further includes an electrically powered alarm element and a pair of electrical contact switch elements which respond to a deviation of the support member from the predetermined position for switching on the alarm. Prior to use, the assembly is capable of assuming a true vertical position within the box-like support and is thereafter fixed in place so that the normally spaced apart contact elements, when in the predetermined position, are brought into contact with one another upon deviation of the support member from such predetermined position. The spacing between the contact elements are adjustable within a predetermined range corresponding to a predetermined range of deviation of the support member.
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