• Cisco IOS Release 12.4(15)T or a later release.

• Cisco Unified IP Phones 7911G, 7941G, 7941GE, 7961G, 7961GE, 7970G, and 7971GE require firmware load 8.2(1) or a later version.

• For the prerequisites for the Enhanced 911 Services for Cisco Unified SRST feature introduced in Version 4.1, see Prerequisites for Enhanced 911 Services..

• Cisco Unified SRST does not support line status speed-dial notification, Call Forward All synchronization, dial plans, directory services, or Music On Hold (MOH).

• Before SIP phone load 8.0, SIP phones maintained dual registration with both Cisco Unified Communications Manager and Cisco Unified SRST simultaneously. In SIP phone load 8.0 and later versions, SIP phones use keepalive to maintain a connection with Cisco Unified SRST during active registration with Cisco Unified Communications Manager. Every 2 minutes, a SIP phone sends a keepalive message to Cisco Unified SRST. Cisco Unified SRST responds to this keepalive with a 404 message. This process repeats until fallback to Cisco Unified SRST occurs. After fallback, SIP phones send a keepalive message every two minutes to Cisco Unified Communications Manager while the phones are registered with Cisco Unified SRST. Cisco Unified SRST continues to support dual registration for SIP phone loads older than 8.0.

Out-of-dialog REFER (OOD-R) enables remote applications to establish calls by sending a REFER message to Cisco Unified SRST without an initial INVITE. After the REFER is sent, the remainder of the call setup is independent of the application and the media stream does not flow through the application. The application using OOD-R triggers a call setup request that specifies the Referee address in the Request-URI and the Refer-Target in the Refer-To header. The SIP messaging used to communicate with Cisco Unified SRST is independent of the end-user device protocol, which can be H.323, plain old telephone service (POTS), SCCP, or SIP. Click-to-dial is an example of an application that can be created using OOD-R.

A click-to-dial application enables users to combine multiple steps into one click for a call setup. For example, a user can click a web-based directory application from his or her PC to look up a phone number, off-hook the desk phone, and dial the called number. The application initiates the call setup without the user having to outdial from his or her own phone. The directory application sends a REFER message to Cisco Unified SRST, which sets up the call between both parties based on this REFER.

For more information about OOD-R, see Out-of-Dialog REFER from the Cisco Unified Communications Manager Express System Administrator Guide.

When you dial a phone, the digit strings must be collected and matched against predefined patterns to place calls to the destination corresponding to your input. Previously, SIP phones in a Cisco Unified SRST system required you to press the DIAL softkey or # key, or wait for the interdigit-timeout to trigger the call processing. This could cause delays in processing the call.

Two new methods of collecting and matching digits are supported for SIP phones depending on the model of the phone:

• KPML Digit Collection

• SIP Dial Plans

The Caller ID display includes the name and number of the caller on the Cisco Unified IP Phone 7911G, 7941G, 7941GE, 7961G, 7961GE, 7970G, and 7971GE. Other SIP phones display only the number of the caller. Also, the caller ID information is updated on the destination phone when there is a change in the caller ID. The change in the caller ID is of the originating party such as with the call forwarding or Call Transfer. No new configuration is required to support these enhancements.

A message displays on the status line of a SIP phone after the phone registers to Cisco Unified SRST to indicate that Cisco Unified SRST is providing fallback support for the Cisco Unified Communications Manager. This message informs the user that the phone is operating in fallback mode and that not all features are available. The default message that displays CM Fallback Service Operating is taken from the phone dictionary file. You can customize the message by using the system message command on the Cisco Unified SRST router. Cisco Unified SRST updates the idle prompt message when you register a SIP phone or when you modify the message through the configuration. The message displays until a phone switches back to the Cisco Unified Communications Manager.

The idle prompt status message supports the Cisco Unified IP Phone 7911G, 7941G, 7941GE, 7961G, 7961GE, 7970G, and 7971GE with Cisco Unified SRST 4.1 onwards. For versions earlier than Cisco Unified SRST 4.1, the phones display the default message from the dictionary file.

Enhanced 911 Services for Cisco Unified SRST enable 911 operators to:

• Immediately pinpoint the location of the 911 caller based on the calling number.

• Call back the 911 caller if a disconnect occurs.

Before this feature was introduced, Cisco Unified SRST supported only outbound calls to 911. With basic 911 functionality, calls were routed to a Public Safety Answering Point (PSAP). The 911 operator at the PSAP would then have to verbally gather the emergency information and location from the caller, before dispatching a response team from the ambulance service, fire department, or police department. Calls could not be routed to different PSAPs, based on the specific geographic areas that they cover.

With Enhanced 911 Services, emergency calls are selectively routed to the closest PSAP based on the caller’s location. In addition, the caller’s phone number and address automatically display on a terminal at the PSAP. Therefore, the PSAP can quickly dispatch emergency help, even if the caller is unable to communicate the location. Also, if the caller disconnects prematurely, the PSAP has the information to contact the 911 caller.

See Configuring Enhanced 911 Services from Cisco Unified Communications Manager Express System Administrator Guide for more information.