Qualstar serves as a librarian for the digital age. The company's products -- tape drives and tape library data storage systems -- house, retrieve, and manage large amounts of data in computer networks. It also provides power supplies (about 45% of sales) that convert AC voltage to DC. Qualstar's systems are compatible with a variety of operating systems and with storage management software from companies such as Symantec. The company, which incorporates tape drives and media from Quantum and Sony into its libraries, sells mainly to manufacturers and resellers. Two customers account for a combined quarter of revenues. Founder and CEO William Gervais owns more than a quarter of Qualstar.