System interfaces22 System functions and features as of R3.0syd-0367/1.3 – R3.0 – 03.20132. 1. 1. 1 Basic rate interface BRI-TBasic access T is suitable for connection to both the public ISDN network and theprivate-leased-line network.2. 1. 1. 2 BRI-S basic rate interface externalThe basic access S external is an BRI-S interface configured as external (S-bus proto-col = EXTERNALS setting in the interface configuration).The basic access S external is designed for the following purposes:• For connection to the private leased-line network or• For connecting DSS1 terminal equipment, which evaluates the DDI number sentby the communication server and routes the call accordingly (e.g. an external faxserver, see also "Direct Dialling Out (DDO)", page 30)Fig. 1 S external in a private leased-line network: PINX-PINX connectionFig. 2 S external in a DDI configurationNote:An BRI-S interface configured as external is a fully-fledged network inter-face and is no longer available as a user-network interface. A basic accessS external cannot be used as a connection to the public ISDN network.
