Jay Forrester invented core memory in 1949 that became the dominant form of computer memory in the 1950s, and remained in use until the late 1970s.
According to public lecture given by Philip Machanick at the University of the Witwatersrand:
"A magnetic material can have its magnetization altered by an electric field. If the field isn't strong enough, the magnetism is unchanged. This principle makes it possible to change a single piece of magnetic material -- a small doughnut called a core -- wired into a grid, by passing half the current needed to change it through two wires that only interesect at that core."Jay Forrester
Jay Forrester was a pioneer in early digital computer development and invented random-access, coincident-current magnetic storage - National Inventors Hall of Fame.
Robert Everett and Jay Forrester were pioneers in the development of early digital computer equipment