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Spira was born in New York City in 1927. He received a Bachelor of Science degree in physics from Purdue University in West Lafayette, Indiana, in 1948 and became a benefactor with his wife, including the School of Mechanical Engineering Ruth and Joel Spira Award and others.
In the 1950s, he worked for an aerospace company, where he was assigned to develop a reliable trigger for atomic weapons. Suggested by others at the laboratory, he called on the thyristor, a solid state semiconductor. During his research, he recognized that the device could also be employed to vary the intensity of light.
A lighting dimmer existed at the time, but was expensive, complicated, and necessitated the use of large rheostats, about 10 in (25 cm) in size. Though there were dimming devices already in use for theater lighting, they were far too big and bulky for use in homes. Spira successfully manipulated a thyristor, a solid-state semiconductor small enough to fit into the wall box that housed a standard light switch. Unlike theatrical dimmers, Spira's standalone device was small enough for home application.
He resigned from his job at the aerospace laboratory to concentrate on refining the device. Spira thence went on to conduct experiments on a ping-pong table in his Riverside Drive apartment in New York City, which led to a device capable of dimming the lighting in a home or office setting.
Spira became—as a result of his discovery—best known for his initial, seminal invention: the first successful solid state-electronic dimmer. He filed for a patent on July 15, 1959 (U.S. 3,032,688). On the basis of the dimmer alone, he and his wife Ruth, who was an active associate, founded the Lutron Electronics Company in Coopersburg, Pennsylvania, in 1961. The privately held firm, whose headquarters remains there today, has grown into an international manufacturer and distributor not only of dimmers, but also of motorized and automated window-covering systems, as well as lighting fixtures and temperature controls.
Spira headed the firm for 54 years and more recently became chair of the board and research director. He died in 2015 at the age of 88 from a heart attack in Springfield Township, Pennsylvania. He was awarded the ASME Leonardo Da Vinci Award in 2000 by the American Society of Mechanical Engineers 
Spira's five principles of industry still make up the backbone of Lutron's business model. The five principles included: