Multi-Site Inbound Redundancy and Shared Telephony

When multiple sites share a PBX, normally you must specify separate hunt numbers and separate ranges of incoming lines for each site to realize speech recognition benefits for incoming callers. However, if the telephony server uses ISDN or SIP signaling protocol and you have configured the PBX properly, you can use the same range of lines for sites that share a telephony server. This allows full use of the lines across multiple sites.

Important: To take advantage of multiple site inbound redundancy features using shared telephony, your PBX must be configured properly and you must have a uniform dialing plan for the sites.

Suppose a deployment has three sites: West Philadelphia, South Philadelphia, and Center City (the principal site). The following table shows the grammars searched for speech recognition at the hunt group prompt when each site has a separate hunt number and all sites share a pool of lines for incoming calls. The system relies on the DNIS to determine which site grammars to use for the incoming call.

Table 1. Shared telephony with one shared pool of lines for all sites
Site	Hunt Numbers	Lines	Grammars Searched
West Philadelphia	215-549-1300 215-549-1301	0-22	West Philadelphia Global
South Philadelphia	215-549-2300 215-549-2301	0-22	South Philadelphia Global
Center City	215-549-3300 215-549-3301	0-22	Center City Global

The following figure illustrates inbound redundancy using DNIS when multiple sites share a VSTG array:

Figure 1. Multiple site inbound redundancy using shared telephony

Someone places a call to a badge user.
The Central Office routes the call.
The PBX skips the VSTG that is down (even though it is in the routing table).
The call is routed to the VSTG that is online.
The call is received by the Vocera Voice Server, which knows which site grammars to use based on the dialed number.
The badge user receives the call.