Sentry - Sentry Industries, Inc. Is a consumer electronic company that started in 1962. It was initially owned by Berkey Photo and operated as a division of Keystone Camera Group. When Philips first introduced the cassette format, Sentry Industries was the second company in the United States to sell cassettes and music industries throughout the United States. 1970 Sentry was re-acquired and became a privately held company. At that time, the company primarily sold pre-recorded tapes, blank tapes, tape players, and accessories. The Sentry brand of tape accessories was sold throughout the United States and expanded into export sales that were successful worldwide. 2009 Sentry opened a showroom in East Kowloon, Hong Kong and the brand is getting worldwide recognition. Today Sentry is one of the largest of types of promotional, mid-priced headphones and ear buds, as well as electronic accessories companies in the world.