teleservice
A teleservice is a telecommunications service for message transmissionthat uses standardized protocols and thus ensures communication between users without restrictions. The exchange of messages is ensured by compatibility.
Teleservices include services that are used for the transmission and forwarding of information in telecommunications networks; this also includes functions that must be available in the terminal equipment. The protocols are defined primarily on the basis of international recommendations by the operators of the public networks. Examples of teleservices include telephone, facsimile, and telex.
For ISDN, teleservices include 3.1 kHz and 7 kHz bandwidth telephony, Group 4 telecopy, data transmission with text and images, data communications with standardized protocols, and videophony. The teleservices for ISDN are defined in ITU Recommendation I.112.