IEC 62680-1-8:2019 is to describe in detail all the Terminal Types that are supported by the Audio Device Class. This document is considered an integral part of the Audio Device Class Specification, although subsequent revisions of this document are independent of the revision evolution of the main Audio Device Class Specification. This is to easily accommodate the addition of new Terminal Types without impeding the core Audio Device Class Specification.
The Audio Device Class Definition applies to all devices or functions embedded in composite devices. All audio signals inside an audio function start at an Input Terminal, pass through some Units, and leave the function through an Output Terminal. Units can manipulate the signal in various ways. Terminals represent the connections of the function to the outside world.
As part of the Terminal descriptor, the wTerminalType field specifies the vendor's suggested use of the Terminal. For example, a pair of speakers is a more suitable target for music output than a telephone line. This feature allows a vendor to ensure that applications use the device in a consistent and meaningful way.