scope:

This ETS specifies a first version of the ISDN - Global System for Mobile communications (GSM) PLMN signalling interface. This ETS is applicable to the first interconnection of PLMN and ISDN. In the future, a new ETS will cover application of the ISDN User Part (ISUP) version 2 on the signalling interface. The ISUP interface being defined is the trunk signalling interface between the PLMN and the ISDN. It is assumed that the interface between PLMN and ISDN can occur in any point in a national network.