The KE-7 was the product of two Swiss designers, Pal de Kiraly and Gotthard End, and was introduced in 1929 by the Swiss manufacturer SIG. It was a recoil operated design and fired from an open bolt. The guns were not adopted by the Swiss military, and were exported primarily to Latin America and China, being mostly made in 8mm Mauser. They were tested by many European nations, and were offered in a wide variety of calibers. The rate of automatic fire would vary depending on caliber, but was not less than 550 rpm. Magazines were typically 25 rounds.
The gun did have a quick-change barrel, and could fire in either single shot or automatic mode. It didn’t use a selector switch, though – pulling the trigger back slightly gave single shots, and a further pull gave automatic fire. This was a relatively common feature of submachine guns at the time, although not seen so much in light machine guns.