W ho made the first commercial scope? Ask any engineer of the 1940s and '50s, and you will doubtless be told that it was DuMont. That's a natural response, since most of the en-gineering-school labs
of the day were equipped with the ac-coupled DuMont 208 or the dc-coupled 304. Engineers learned about oscilloscopes in those laboratories.

There were other manufacturers. But they didn't have a significant impact on the professional market. Engineering schools had DuMonts, and when engineers moved into industry, it was natural to specify the instruments they already knew. In those days, it wasn't Tektronix or HP. They came later.

In March 1948, DuMont dominated the scene. At the annual show of the Institute of Radio Engineers, a predecessor to the Institute of Electrical andElectronics Engineers, Dr. Allen Balcom DuMont wandered over to the 10-foot Tektronix booth. Howard Vollum, that company's co-founder and president, had introduced his first scope at the show.

Dumont fooled with the knobs on the Tektronix 511. He admired the scope, the first to include triggered sweep, calibrated vertical amplifier and calibrated time base. The man who owned the scope business turned to Vollum and offered this avuncular evaluation: "That's a nice scope, son. But nobody's ever going to spend $700 for an oscilloscope." At the Allen B. DuMont Laboratories, the going wisdom was that Tektronix would never survive, that shipping charges from Oregon would kill the company.

Giv en DuMont's dominance in the scopes, it was easy to assume that Allen B. had started the business. In fact, he didn't win the scope business; it was handed to him by an early departure-General Radio.

Origins of DuMont
DuMont started his company in late 1931 after leaving DeForest Radio Co. in Passaic, N. J., where he had been chief engineer and where he developed technology for manufacturing vacuum tubes and pursued television technology. DuMont's new company, in the basement of his home in Upper Montclair, N. J., began manufacturing cathode-ray tubes and later also made cathode-ray oscilloscopes. By 1937-38 the company was also becoming a major producer of TV receivers. It was first to introduce large-screen (14-inch) TVs and in 1939 had 14-inch sets at the New York World's Fair where others had 7-inch sets. Later, DuMont made a name in television transmitters and studio equipment and started a separate business, DuMont Broadcasting Corp., which operated television stations. It was sold in 1955 and later became Metro-Media Broadcasting.

In early 1931, the year DuMont started his business, the General Radio Co. of Cambridge, Mass., (now GenRad of West Concord, Mass.) marketed the Electron Oscillograph, Type 535-A. (GR, as the company was known, didn't have model numbers; it had type numbers.)

The 535 first used cathode-ray tubes made by Manfred von Ardenne in Germany, then later used CRTs made by Westinghouse. The instrument came in two parts. The CRT was mounted on a stand and the power supply in a separate cabinet. Since the company used its own sales force, not reps, it felt free to include price lists in its catalog. The CRT, its mounting stand and the power supply sold for $280.

Before long, the company added, in a separate $170 box, the Type 506-A Bedell Sweep Circuit. It had been developed by Professor Frederick Bedell of Cornell University, a pivotal figure in the early world of oscilloscopes. At first, GR licensed the sweep-circuit patent from Bedell. Later it bought the pat ent, retained the instrument rights and sold the entertainment rights to RCA for use in television receivers.

The General Radio 535, while it was the first scope from an important manufacturer and the first that almost everybody knew about, was not quite first. An earlier one was developed in 1927 by Bedell (yes, the same Bedell) and Herbert Reich of Cornell. A small number, estimates run from six to 12, were manufactured by R. C. Burt Scientific Laboratories of Pasadena, Calif. Robert Burt had been a scientist at Bell Labs in New York, a specialist in glass blowing for CRTs. He became a professor at CalTech and he married Eleanor Bedell, the professor's daughter.

So Frederick Bedell was the most influential figure in early scopes. With Herbert Reich, he designed a scope at Cornell. A student who studied for his doctorate under Bedell, Thomas T. Goldsmith Jr., became DuMont's director of research in 1936. His son-in-law, Robert Burt, ran the first scope business, though it didn't last long and went al most unnoticed. And Bedell provided a sweep circuit for General Radio.

General Radio's big move
General Radio's big move came in 1934, when it announced the Type 687-A Electron Oscillograph. A complete scope, the 687-A included CRT, power supply and sweep circuit, all in one housing. Deflection sensitivity ranged from 1 V/ to 5 V/, a linear function of anode voltage, which could be adjusted from 500 to 2,500 V. By today's standards, the instrument was far from sensitive, since signals were applied directly to the deflection plates. Plate capacitance was specified as less than 1.5 F. This was before micro-micro became pico and before units derived from a person's name (like the farad from Michael Faraday) were spelled out lower case and abbreviated with an initial (and most often single) capital letter. Today that capacitance would be 1.5 pF. The frequency range was specified-rather modestly. "Even at frequencies of 30 megacycles per second," a catalog supplement proclaimed before hertz was i nvented, "the envelope patterns are fairly good, especially when the radio-frequency deflection is used in one direction only and the time axis obtained with a rotating mirror or a moving film camera."

The 687-A was followed by the 770-A, with more-advanced features, but the 770-A wasn't marketed. GR executives decided that it was too difficult to manufacture and too costly for the probable market, radio-service technicians, which the company chose not to serve. Before the surge occurred in CRT development for radar with the onset of World War II, GR dropped out of the scope business.

In A History of the General Radio Company , commemorating its 50th anniversary in 1965, Arthur E. Thiessen, chairman of the board of directors, made a poignant observation about the decision not to stay in the oscilloscope business: "This was a considerable error in product judgment."

By 1935, scopes were being made by Ge neral Radio, DuMont, General Electric and Radio Corporation of America. And DuMont kept growing. In 1958, Allen DuMont assigned his research director, Thomas Goldsmith, to find a merger partner.

In 1960, Fairchild Camera and Instrument Corp. acquired DuMont Laboratories. By this time, it consisted of the tube operation, which included monochrome CRTs and photomultiplier tubes, and the oscilloscope operation. The broadcast operation had already been sold and the Emerson Radio Corp. had taken over the TV-receiver business. Five years later, in 1965, DuMont died at the age of 64. A year later, Goldsmith left to become a professor of physics at Furman University in Greenville, S.C., his hometown.

Fairchild's board by no means had been unanimous in acquiring DuMont, which was suffering huge losses. John Carter, board chairman, swung the vote in favor of the purchase. Later, Fairchild sold the tube operation to Thomas Electronics and retained instrumentation.

By 1968, with Carter no longer at Fairchild, the company sold the remains of DuMont to a liquidator, International Fastener Research. The liquidator found a customer for DuMont-John Carter.

A name change
Fairchild would not permit use of the original name, Allen B. DuMont Laboratories. So Carter's company came to be known as DuMont Oscilloscopes. In West Caldwell, N.J., the home of its predecessor, DuMont Oscilloscopes took over the older scopes and began to design a new line. Within three years, Carter, who owned the company but did not manage it, died. His son, John Carter Jr., came in to manage the business. He started another company, DuMont Instrumentation, in Commack, N.Y., which became the parent of DuMont Oscilloscopes and a California semiconductor company, both drains on the company's funds. In 1984, DuMont Instrumentation went bankrupt. The bankrupt company was bought by Ed Petrasek, who had been general manager of DuMont Oscilloscopes, and Richard Blackwell. Today, the company, E and R (for Ed and Richard), does business a s DuMont Oscilloscopes.

For help in providing information for this report, special thanks are due to Rudy Feldt, former General Manager; Sam Christaldi, PhD, former General Manager; and Fred Katzmann, former General Manager of the Instrument Division of Allen B. Dumont laboratories; Dr. Thomas T. Goldsmith Jr., former Director of Research of Allen B. Dumont laboratories; Ken Hoagland, former Research Scientist and former Chief Engineer of the Dumont Tube Division; Elliott Sivowitch, Museum Specialist of the Electrical Collection of the Smithsonian Institution National Museum of American History; Thomas C. Vales, Curator of the General Radio Museum; and Peter A. Keller, a CRT Specialist at Tektronix.

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