 Ferrite logic circuits are inherently more stable than vacuum tubes and transistors, draw no power when unused, and are impervious to electromagnetic interference.In 1959, Crane introduced the all-magnetic logic approach at the Fall Joint Computer Conference, eventually leading to a demonstration of the world's first all-magnetic computer in 1961.The technology was soon commercialized by Aircraft Marine Products (AMP) Inc., under license from SRI, and used primarily in the rapid transit system of New York City and at railroad switching yards, where electro-magnetic interference made electronic computers unfeasible.