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Design Guide for Cisco Unity Release 5.x
OL-14619-01
Chapter 6 Integrating Cisco Unity with the Phone System
Integrating with Cisco Unified Communications Manager Express (by Using SCCP or SIP)
Figure 6-10 Cisco Unified Communications Manager Fallback with BRI or PRI
When the WAN is down and Cisco Unity has foreign exchange office (FXO) or foreign exchange station
(FXS) access connect to a public switched telephone network (PSTN), Cisco
Unity uses in-band dual
tone multifrequency (DTMF) signaling (see
Figure 6-11).
Figure 6-11 Cisco Unified Communications Manager Fallback with PSTN
In both configurations, phone message buttons remain active and calls to busy or unanswered numbers
are forwarded to Cisco
Unity. The installer must configure access from the dial peers to the voice-mail
system, and establish routing to Cisco
Unity for busy and unanswered calls and for the message button.
If Cisco Unity is accessed over FXO or FXS, you must configure instructions (DTMF patterns) for
Cisco
Unity so it can access the correct voice-mail system mailbox.
When using Cisco Unified SRST with Cisco Unity, the integration has the following limitations during
a WAN outage:
IP
IP
IP
88981
Cisco CallManager
Voice-Mail Server
CM Gateway
BRI/PRI
SRST Gateway
WAN
WAN F
AN F
ailureWAN F
AN F
ailureWAN Failure
IP
IP
IP
88980
Cisco CallManager
Voice-mail server
Cisco CallManager gateway
FXS
PSTN
FXO
WAN
WAN failure
Call forward to busy greeting
When the Cisco Unified SRST router uses FXO/FXS connections to the
PSTN and a call is forwarded from a branch office to Cisco
Unity, the
busy greeting cannot play.