Jan Rajchman holding a 256-bit magnetic core memory array, which he assembled at RCA’s Princeton laboratories in the early 1950s. (David Sarnoff Library Collection, Hagley Museum and Library)

Jan Rajchman holding a 256-bit magnetic core memory array, which he assembled at RCA’s Princeton laboratories in the early 1950s. (David Sarnoff Library Collection, Hagley Museum and Library)

Jan Rajchman

AUGUST 10, 2020

Scientist of the Day - Jan Rajchman

Jan Rajchman, an electrical engineer and inventor, was born to a distinguished Polish family in London on August 10, 1911. His grandfather, Aleksander Rajchman, helped establish the Warsaw Philharmonic, while his father, Ludwik Rajchman, was a bacteriologist who later served as the first chairman of the United Nations International Children’s Relief Fund (UNICEF). When Jan was seven years old, his family returned to Poland for a few years before relocating to Geneva, where Ludwik secured a position with the League of Nations. While attending the Collège de Genève, a secondary school established by John Calvin in 1559, the younger Rajchman demonstrated a talent for physics and mathematics. He enrolled in the Swiss Federal Institute of Technology and earned a degree in electrical engineering in 1934.

After graduation, Rajchman traveled to the United States in order to secure a position at the Radio Corporation of America (RCA). In the 1930s, RCA was one of the leading American electronics firms, and Rajchman was eager to work with Vladimir Zworykin, who had recently demonstrated his iconoscope television camera. After interviewing at RCA’s laboratories in Camden, New Jersey, Rajchman learned there were no jobs available. Disappointed by this news, he traveled to Boston and enrolled in a summer session at the Massachusetts Institute of Technology in order to improve his English. In the fall of 1935, he received a telegram informing him that there was an opening available in Camden. Rajchman caught a train to New Jersey the next day. He would remain a member of RCA’s technical staff for the next four decades.

Rajchman was initially assigned to study the electron multiplier tubes that Zworykin used to amplify the iconoscope’s video signals. Following the invasion of Poland in 1939, he became involved with a new project to improve the fire control systems in American antiaircraft guns. The military also hoped that advances in electronics could aid in the compilation of ballistics tables and approached RCA about the possibility of constructing a machine to streamline that process. Ultimately, Zworykin decided RCA should not oversee that project, but members of his team, including Rajchman, consulted with personnel at the University of Pennsylvania’s Moore School of Electrical Engineering as they started designing ENIAC (Electronic Numerical Integrator and Computer): the first general-purpose, programmable, electronic computer.

These conversations paved the way for Rajchman’s participation in future computing projects. After relocating to RCA’s new research laboratories in Princeton, he collaborated with John von Neumann to create a memory system for a computer being built at the Institute for Advanced Study (IAS). To that end, Rajchman designed a vacuum tube containing a rectangular mesh of horizontal and vertical wires. By applying a voltage to a particular combination of wires along each axis, he could block the passage of electrons through certain squares of the grid, with each square corresponding to a bit of information. Rajchman referred to his invention as a selective electrostatic storage tube, or Selectron, and it was one of the earliest forms of digital random access memory (RAM).

Rajchman’s work attracted a great deal of attention within the newly emerging computing community. He even delivered a lecture on the Selectron at a special summer school hosted by the Moore School in 1946. Rajchman originally believed the tube would have a storage capacity of 4,096 bits of RAM, but manufacturing difficulties forced him to reduce that figure to 256 bits. These production delays led Von Neumann to adopt another memory system for his project, but the IAS machine would later serve as a model for computers around the world—and several of these spinoff systems relied on Selectrons.

The Selectron was an impressive piece of engineering, but the complexity of its design and the difficulty associated with scaling up its size led Rajchman to explore other ways to store digital information. The most promising of these was core memory, which consisted of a wire matrix with small rings of magnetic material at each intersection. As in the Selectron, it was possible to target a specific intersection on the grid by applying a voltage to both a horizontal and vertical wire. In this case, doing so caused the direction of the chosen core’s magnetic field to switch direction, corresponding to either a 1 or 0 in binary code. Magnetic core memory was faster and cheaper to manufacture than previous data storage systems and remained the dominant form of computer memory until the introduction of semiconductor RAM in the 1970s.

Rajchman filed a patent for his invention in September 1950 and later constructed a 256-bit core memory panel (first image). He quickly discovered that he was not the only one thinking about the use of magnetic cores to store digital information. By the early 1950s, an amateur inventor named Frederick Viehe, Harvard physicist An Wang, and MIT engineer Jay Forrester had filed patents for similar inventions, leading to an extended legal battle to determine who deserved credit as the inventor of core memory.

As this patent litigation worked its way through the courts, Rajchman continued to experiment with magnetic memory systems. One byproduct of these efforts was a new form of magnetic core, which had more than one hole. He determined that this new circuit component, which he called the “transfluxor,” could do more than simply switch between 0 and 1; it could also store any intermediate value in between.

Rajchman envisioned a variety of possible uses for transfluxors in computing and communication systems. But perhaps the most exciting application he found for his new invention was in flat-panel displays. David Sarnoff, the chairman of RCA, had recently challenged his technical staff to develop a replacement for the television picture tube. Rajchman realized that transfluxors, in combination with addressing circuitry inspired by his work on core memories, could be used to produce grayscale images. By 1955, he was able to construct a functional 1200-element display using electroluminescent phosphors (second image). The image was monochrome and low-resolution, but it confirmed the possibility of presenting moving electronic images on a flat screen.

Rajchman initially hoped to improve upon his flat-panel display, but other projects took priority, especially after he was appointed the first head of RCA’s Computer Research Laboratory in 1961. In that capacity, he encouraged further research into magnetic and semiconductor memories, as well as new data storage systems based on superconductivity and holography. After RCA withdrew from the computer industry in 1971, Rajchman remained on part of the management team, supervising the company’s research laboratories in Zurich and Tokyo.

By the time he resigned from RCA in 1976, Rajchman had secured over 100 patents, including his 1950 description of core memory. Unfortunately, although the courts initially agreed that he should receive credit for creating this vital technology, RCA chose to withdraw its priority claims in 1964 as part of a licensing agreement with MIT and IBM. As a result, Rajchman’s inventions are sometimes overlooked by historians of computing. The same cannot be said, however, for the consumer electronics industry, which views his transfluxor-driven display as a direct ancestor of the screens that surround us in our homes and offices. In recognition of this foundational work, the Society for Information Display’s annual award for outstanding research related to flat-panel displays is named the Jan Rajchman Prize.

Benjamin Gross, Vice President for Research and Scholarship, Linda Hall Library. Comments or corrections are welcome; please direct to grossb@lindahall.org.