This ETS specifies the end-to-end protocol to support the telephony 7 kHz teleservice when connected by the pan-European ISDN, as provided by European public telecommunications operators. And end-to-end protocol provides the mechanism to support user-data transfer between user applications. This ETS is applicable to terminal equipment, and other equipment (e.g interworking units, conference bridges), supporting the telephony 7 kHz teleservice.