Cisco Cisco IOS Software Release 12.4(2)XB6

Cisco Unified IP Phone 7961G

Cisco Unified IP Phone 7961G-GE

IP phone authentication for secure Skinny Client Control Protocol (SCCP) signaling between 
Cisco Unified CME and IP phones

Fax passthrough mode using Cisco VG 224 voice gateways, Analog Telephone Adaptors (ATA), and 
SCCP

Video support 

QSIG integration with TDM PBXs

Feature access codes and feature control

Redundant Cisco Unified CME router

For details about new features, see the “Feature History” chapter of the Cisco Unified CallManager 
Express System Administrator Guide at the following URL:

For links to all Cisco Unified CallManager Express documents, see the documentation roadmap at the 
following URL:

Cisco Unified Survivable Remote Site Telephony (SRST) 4.0 adds these features to the Cisco 1700 
series routers in Cisco IOS Release 12.4(4)XC:

Support for the following Cisco Unified IP Phone models:

Cisco Unified IP Phone 7911G

Cisco Unified IP Phone 7941G

Cisco Unified IP Phone 7941G-GE

Cisco Unified IP Phone 7961G

Cisco Unified IP Phone 7961G-GE

Cisco IP Communicator support 

Fax pass-though for ATA and Cisco VG 224 and Cisco VG 248 using SCCP mode. 

H.323 VoIP call preservation enhancements for WAN link failures 

Video support 

For more information about these features, go to 

There are no limitations or restrictions in this release.