General Radio Company - Products - Oscilloscopes

Genral Radio Company - Products - Oscilloscopes

General Radio’s role in the ‘Scope industry is not widely known. Here is a shortened version of the story.

	In 1931 there were several ways of observing electrical waveforms. One was to apply different signals to the deflection plates of a cathode-ray tube. Such tubes were available at the time and used by many experimenters. General Radio provided the first commercial version of such a device in 1931 with tubes, first from Germany, and later from Westinghouse, U.S. The instrument was in two pieces with the tube mounted on a stand and the power supply in a separate cabinet.
	The resulting patterns were not deemed very useable, however without a method of stretching the display out over a time line to form an “oscillogram”. A more useful method was to apply the signal to a “string”, a fine wire located in a magnetic field. The resulting wiggles of the wire could be converted into a view of amplitude versus time in two ways. One was to project a shadow of the wire onto a mirror which rotated at some speed synchronous with the signal. The reflected image would form a pattern of amplitude versus time. An even better way (at the time), which would also provide a “recording” of the signal, used a camera to photograph the shadow on a continuous strip of photographic film or paper which was drawn through the camera at a constant rate.
Such a String Oscillograph was first offered in 1928 and, with camera added, was described by General Radio Engineer Horatio W. Lamson (M.I.T. 1915, Harvard 1917) in April 1931. Rotating mirrors and film were also used with the CRT Oscillograph. The “picture” changed however, with the invention of the linear sweep circuit by Professor Bedell of Cornell.
	GR offered the Type 535A Electron Oscillograph with the licensed Type 506A Sweep Circuit in 1931 and, finally, purchased the patent and produced the self-contained Type 687A designed in 1934 by E. J. Karplus (Vienna Institute, 1923) and H.H. Scott (M.I.T. 1930). A more refined version, the Type 770, was designed by D.B. Sinclair (M.I.T.1931), but never marketed. GR management felt the product too expensive and difficult to manufacture, and with a limited market. They sold the entertainment rights to David Sarnoff’s RCA, thus helping to start the TV industry, and the instrumentation rights to Allen B. Dumont who became the leader in the Oscilloscope industry until toppled by Tektronix in the 50‘s. The ‘scope industry really didn’t get going until after WWII. The advances in Radar technology sponsored by the war effort allowed Dumont and Tektronix to produce great products - too late for GR. Later GR management regretted their “error in judgment”. Oh, well.

CONTENTS:

>GR “EXPERIMENTER”

>CATALOGS & BULLETINS

General Radio and Teradyne Logos

copyright © Teradyne, Inc. 2003