To resolve the issue, add this configuration:
voice-card 1
no local-bypass
!
This command changes the default behaviour of the voice card and keeps the DSP across the audio stream for the duration of the call, even if the call is later connected directly to another voice port on the same network module. Therefore, the Supervisory Disconnect Tone feature is active as expected.
In order to speed up the disconnection if the Supervisory Disconnect Tone feature is used, issue these commands to the voice port configuration:
timeouts call-disconnect 5
timeouts wait-release 5
These settings shorten the time the router waits before it determines that the call needs to be dropped due to disconnect tones played by the network. The normal Cisco IOS? defaults are 30 and 60 seconds respectively, so these reduce the drop time to 5 seconds:
For further information on Supervisory Disconnect Tone problems, refer to these documents
http://www.cisco.com/en/US/tech/tk652/tk653/technologies_tech_note09186a00800ae2d1.shtml