The moving slip ring surface of electrical machinery transfers electrical current by contact thereof with liquid metal directly or through the tips of a plurality of closely spaced brushes positioned along the bottom of a housing under pressure within which the liquid metal is contained. The brush tips are respectively connected to lower ends of fibers electrically interconnected within the housing and exposed to the liquefied metal received and retained within the housing. According to one embodiment, the liquefied metal is retained within containment material filling the housing for contact exposure of the fibers therewith. According to another embodiment, exposure of the fibers to the liquefied metal within the housing is effected by entry of the liquefied metal into hollow brush tubes connected to and extending from the bottom of the housing, through which stem portions of the fibers extend to the brush tips.


> In-situ calibration of radar frequency measurement

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