There are three classes that make up the definition for communication devices: the Communication Device Class,Communication Interface Class and the Data Interface Class. The Communication Device Class is a device level definition and is used by the host to properly identify a communication device that may present several different types
of interfaces. The Communication Interface Class defines a general-purpose mechanism that can be used to enable all
types of communication services on the Universal Serial Bus (USB). The Data Interface Class defines a generalpurpose
mechanism to enable bulk or isochronous transfer on the USB when the data does not meet the requirements
for any other class.
1.1 Scope
Given the broad nature of communication equipment, this specification does not attempt to dictate how all
communication equipment should use the USB. Rather, it defines an architecture that is capable of supporting any
communication device. The current release of the specification focuses on supporting connectivity to
telecommunication services (devices that have traditionally terminated an analog or digital telephone line), and medium
speed networking services (“Always Connected” LAN/WAN media types). The specification currently outlines the
following types of devices:
x Telecommunications devices: analog modems, ISDN terminal adapters, digital telephones, and analog
telephones
x Networking devices: ADSL modems, cable modems, 10BASE-T Ethernet adapters/hubs, and “Ethernet”
cross-over cables.
This specification does not attempt to redefine existing standards for connection and control of communication services. The Communication Class defines mechanisms for a device and host to identify which existing protocols to use. Where possible, existing data formats are used and the transport of these formats are merely enabled by the USB through the definition of the appropriate descriptors, interfaces, and requests. More specifically, this specification describes a framework of USB interfaces, data structures, and requests under which a wide variety of communication devices can be defined and implemented.