| 摘要 |
A chamber filled with an oscillation damping liquid has a non-magnetic plumb bob suspended from an upper portion of the chamber and a radiated beam path traverses the chamber below the suspension point of the freely suspended plumb bob. The beam path and plumb bob are arranged in a desired relationship whereby in order for the suspending member of the plumb bob to completely block the beam path the chamber, or the body on which it is mounted, must be in a desired predetermined position, such as a true horizontal or a true vertical position. An electric power source and circuitry is provided to operate in response to blocking of the beam path to provide a desired electrical output indicating the desired predetermined position has been achieved and is being maintained. The electrical output may be used to operate visual or aural indication emitting device to notify the user when the desired position is achieved. A desirable application is mounting one or more chambers or detectors to an elongated body appropriate for use as a builder's level.
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