A digital switch is a device that handles digital signals generated at or passed through a telephone company central office and forwards them across the company's backbone network. It receives the digital signals from the office's channel banks that have been converted from users' analog signals and switches them with other incoming signals out to the wide area network.
Digital switches are described in terms of classes based on the number of lines and features that are provided. A private branch exchange (PBX) is a digital switch owned by a private company. A centrex is a digital switch at the central office that manages switching for the private company from the central office.