A SURVEY OF EARLY POWER TRANSISTORS by Joe A. Knight IBM 1950s GERMANIUM POWER TRANSISTORS
	AT LEFT: This was one of several identical devices that were acquired from the estate of someone who had "worked at IBM" in New York somewhere.  The marking gave no clue as to it's function or use.
ABOVE: This is what was found once the outer case was removed.  The interior matches exactly the devices described in the references on the previous page. The gray resin filled top concave surface can just be seen on the left device. This covers up the exhaust hole for the hermitic sealing. While the X-4 was a truly unique power device, it is not known what the IBM final production designation was for the X-4 or how long IBM used it in future computer designs.  It may have evolved into other physical configurations as time went along.  It could also be that as computer designs rapidly evolved with further transistor development that the need for this type of power transistor was no longer needed by the later 1950's and so faded into the background as another semiconductor historical oddity.
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