PJ-11

Page 48 of the book "The Story of Electronics Development at the General Electric Company " lists this tube as a "Special type of PT240" but does not state the differences. These tubes are industrial versions of the UX240.

In an article in "Radio Engineering" for March 1933, Albert W Hull of the GE research Laboratories discusses this tube. In the article he states that "it could measure voltages ten times smaller than could be detected before" and with tube noise "Part of the tube noise we now understand and recognize as fundamental" and " The result is the PJ-11 with low frequency input noise level of less than one half a microvolt, as compared to about 10 times this value for the best tube previously available. No one knows what will be done with this modest addition to the tube family. The possibility of amplifying and observing things ten times smaller than before suggests new discoveries".