The FXO interface of VoIP devices is suitable for connecting to a PSTN-PBX in order to expand the amounts of extensions. The Vigor VoIP routers with FXS interface also provide useful ways to implement a similar utilisation. The following are two typical application scenarios.

Case 1: Calls from VoIP to extension.

1. David dials the VoIP number of Vigor2900V(A).

2. After connection success, presses Linda’s extension 610.

Case 2: Calls from extension to VoIP.

1. Linda presses prefix number (e.g. “7” ) firstly to choose exterior line – FXS of Vigor2900V(A).

2. Then dials David’s VoIP number of Vigor2900V(B).

Note : PSTN-PBX is widely adopted by most AnnexA countries. Because most AnnexB countries such as Germany, Norway and the Netherlands have encouraged small offices to deploy ISDN PRI into PBX, PRI PBX are quite popular at offices located in Germany, the Netherlands and Norway.