Signedetched and white filled on front panel: ELECTRON OSCILLOGRAPH / AND / BEDELL SWEEP CIRCUIT / TYPE 687-B SERIAL NO. 286 / GENERAL RADIO CO. / CAMBRIDGE, MASS. / U.S. PATENT 1,707,594
Inscribedstamped in white on top: 12
FunctionThe electron oscillograph is an electronic device that is used to observe rapidly varying signal voltages as a graph on a screen.
Oscilloscopes and oscillographs are most often used to detect the exact wave shape of an electric signal.
For more information on the function of oscilloscopes, see the wikipedia page here.
General Radio was one of the initial developers of the oscillograph, and starting in 1934, it produced the 687A type, which was the first to integrate the Sweep Circuit invented by Professor Frederick Bedell of Cornell University. This is the electronic system that allows the oscillograph to stretch the (up-and-down) voltage fluctuations on the screen as a graph. Until then, watching the wave pattern required the use of additional visual mechanisms such as a string oscillograph and rotating mirrors or cameras.
The instrument was not perceived by General Radio as having much commercial potential, and the rights to its development were sold to RCA and DuMont, which used them to develop Television and the Oscilloscope respectively.
ProvenanceFrom the Physics Dept. Bowdoin College, Brunswick, Maine. Collected on May 14, 1991. Courtesy of Prof. Elroy Lacasce.