In 1942, the company changed its name to Sylvania Electric Products Inc. During World War II, Sylvania was chosen from among several competing companies to manufacture the miniature vacuum tubes used in proximity fuze shells due to its quality standards and mass production capabilities.

Sylvania developed the earliest flash cubes for still cameras, later selling the technology to Eastman Kodak Company, and later a 10-flash unit called FlipFlash, as well as a line of household electric light bulbs, which continued during GTE's ownership, later sold off to the German manufacturer Osram, and is today marketed as Osram Sylvania.

In June 1964, Sylvania unveiled a color TV picture tube in which europium-bearing phosphor was used for a much brighter, truer red than was possible before.

[3] Through merger and acquisitions, the company became a significant, but never dominating supplier of electrical distribution equipment, including transformers and switchgear, residential and commercial load centers and breakers, pushbuttons, indicator lights, and other hard-wired devices.

At the time, they were the leading supplier of vacuum cast coil transformers, manufactured in their Hampton, Virginia plant.

Their patented design used bus bar encapsulated in a thin coating of epoxy and then bolted together across all three phases, using special non-conductive fittings.

By 1981 GTE had made the decision to exit the electrical distribution equipment market and began selling off its product lines and manufacturing facilities.

The Sylvania Electric Products explosion, which involved scrap thorium, occurred on July 2, 1956, at their facility in Bayside, Queens, New York City.