Description:
A crystal detector, consisting of a marble based with metal fittings that hold a piece of semiconducting mineral in a fixed position so that an electrode can be passed over it to detect a radio signal used for telegraphic transmission.
The marble base of this detector is rectangular, with a metal disk-shaped stage which supports a well that holds the mineral sample. The stage may be adjusted means of two long screws with cylindrical rubber knobs and a third rod, which protrudes from the stage. The mineral in the well may be galena, or crystallized lead sulfide, which was a commonly used early semiconductor.
Two metal posts are mounted at the other end of the base; they support a pair of triangular arms perpendicular to the base. The arms hold a screw in position over the mineral sample, so that it could be adjusted to make contact with the mineral.
There are two binding posts mounted on the marble base, with knurled edge adjustment screws.