Part 1: Basic SRST Configuration
Part 2: SRST Configuration: IP Phone Clock, Date, and Time Formats
Part 3: SRST Configuration: IP Phone Language Display
Part 4: SRST Configuration: IP Phone Customized System Messages
Part 5: SRST Configuration: Secondary Dial-Tone
Part 6: SRST Configuration: Dual and Octo Line Phones
While in SRST mode, phones that are in fallback mode quite often are not configured to have the same dial-plan as when they are registered to the CUCM (call manager). Where the CUCM typically will hold the larger, centralized dial-plan; the SRST gateway rarely has the same expansive dial-plan found in the CUCM. In fact, the SRST gateway is often used to provide simply local dialing between registered phones, emergency service, and PSTN access.
It may be determined that it is more comforting for users to hear a secondary dial-tone while in fallback mode. In this case, after they dial an access code, "9", for example, the user will be presented with a audible dial-tone that indicates that they are ready to place a call directly to the PSTN.
Router(config-cm-fallback)# secondary dial-tone 9