The innovative LANCOM 1722 VoIP is a first in providing an all-round solution for convergent (i.e. integrated data and voice) site connectivity that especially addresses the connection of smaller external sites, home offices and branches. The LANCOM 1722 VoIP is a voice migration appliance that actively binds existing ISDN telephones or smaller PBXs into new communications structures via an ISDN-to-LAN interface. This device recognizes the cheapest way of placing a call and automatically switches between ISDN and VoIP. This means, for instance, that incoming and outgoing local calls can be directed to the WAN-side ISDN interface of the LANCOM 1722 VoIP. Expensive long-distance calls are automatically transferred from ISDN to VoIP. To route a call, the router decides whether an outgoing call is best routed via the central VoIP gateway at company headquarters, via a provider's VoIP gateway, or via the WAN-side ISDN interface. If, for example, the company headquarters with the VoIP server is located in Southampton, then the VoIP gateway at the Birmingham branch must be cable of excluding local Birmingham calls (by ISDN break-out) to prevent expensive long-distance calls being made from headquarters in Southampton. Telephony makes extreme demands on high availability, and LANCOM addresses these demands with extensive backup solutions for routers and connections. Even in the case of a power cut, the LANCOM 1722 VoIP offers lifeline support. A power failure causes the router to automatically switch back to communications via the ISDN telephone network.