264 U . S . BUREAU OF STANDARDS NOTES. [J. F.I.

B I B L I O G R A P H Y OF S C I E N T I F I C L I T E R A T U R E R E L A T I N G TO H E L I U M ) ~

THE first edition of the Bibliography of Scientific Literature relating to helium has been revised, and references to the literature published during the years 1919--1921 have been added.

As in the first edition, the titles are grouped under numerous headings and so arranged under each heading that related articles will appear together in their chronological order. Approximately 600 references are given of which about one-third have been added since the first edition.

D E S C R I P T I O N A N D O P E R A T I O N OF AN E L E C T R O N T U B E D E T E C T O R U N I T F O R R A D I O R E C E P T I O N Y

[ABSTRACT.]

THE apparatus now in use for radio reception, except the most simple types, uses electron tubes. This circular is one of a series of circulars on the construction of simple receiving sets. Bureau of Standards Circulars Nos. I2O and I2I were the first two of this series. Very simple receiving sets such as those described in Circulars Nos. I2O and I2I may use a crystal detec- tor instead of an electron tube. For a description of the electron tube and the principles of its operation reference may be made to " The Principles Underlying Radio Communication," Signal Corps Radio Communication Pamphlet No. 4o.

Electron tubes are used for reception in many different kinds of circuits. One of the most elementary is as a simple detector. It is also possible to use electron tubes in reception in circuits using various kinds of amplification, or regeneration, heat recep- tion, or other methods. For descriptions of various kinds of tube receiving circuits, reference may be made to the book, " The Principles Underlying Radio Communication," or to one of various other books now available, of which a list may be found in Bureau of Standards Circular No. I 2 2 (price, 5 cents). A simple tube detector set will not serve to receive signals trans- mitted by continuous wave radio telegraphy.

This circular describes a simple electron tube detector receiv . . . . ing set and gives a method of operating it. This set with electron

:" Circular, No. 8I. 1~ Circular, No. I33.