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![Photoelectric ray to determine flying ceiling. Washington, D.C., June 15. To permit a ground observer to determine at what height flying is safe during days of fog and heavy overcast, Miss Elizabeth M. Zandonini, of the Radio Section staff of the Bureau of Standards, is shown with the balloon transmitting equipment. A photoelectric cell measuring light brightness is used to control the pitch of the radio signal transmitted from the balloon as it ascends. A graphical frequency recorder plots the pitch and hence [...] a measure of the light brightness as a function [...] height. The experiments are carried on for the U.S. [...]](https://cache.getarchive.net/Prod/thumb/cdn4/L3Bob3RvLzE5MzcvMDEvMDEvcGhvdG9lbGVjdHJpYy1yYXktdG8tZGV0ZXJtaW5lLWZseWluZy1jZWlsaW5nLXdhc2hpbmd0b24tZGMtanVuZS0xNS10by1wZXJtaXQtMTAyNC5qcGc%3D/40/49/webp "Photoelectric ray to determine flying ceiling. Washington, D.C., June 15. To permit a ground observer to determine at what height flying is safe during days of fog and heavy overcast, Miss Elizabeth M. Zandonini, of the Radio Section staff of the Bureau of Standards, is shown with the balloon transmitting equipment. A photoelectric cell measuring light brightness is used to control the pitch of the radio signal transmitted from the balloon as it ascends. A graphical frequency recorder plots the pitch and hence [...] a measure of the light brightness as a function [...] height. The experiments are carried on for the U.S. [...]")
Photoelectric ray to determine flying ceiling. Washington, D.C., June ...
A black and white photo of a woman putting something in a box. Public domain portrait photograph, free to use, no copyright restrictions image - Picryl description
Comrades, all around is brightness sheet music
Music associated with the Union side
Comrades, all around is brightness sheet music
Music associated with the Union side
Comrades, all around is brightness sheet music
Music associated with the Union side
Comrades, all around is brightness sheet music
Music associated with the Union side