scope:

This European Telecommunication Standard (ETS) defines the Terrestrial Trunked Radio (TETRA) system supporting Voice plus Data (V+D). It specifies the stage one to three of the TETRA gateway to Public Switched Telephone Network (PSTN). Stage one is an overall service description from the user's point of view, but does not deal with the details of the human interface itself. The PSTN gateway establishes a basic call, when SwMI detects an outgoing call from a TETRA user to PSTN or the PSTN gateway detects an incoming call from PSTN to a TETRA user. The PSTN gateway ensures that basic signalling required in the operation of the TETRA call and the PSTN call is maintained across the gateway.