Core Issue
The Cisco Analog Telephone Adaptors (ATAs) are being used as H.323 gateways in Cisco CallManager 3.1.2c.
This occurs in two scenarios:
- Calling between two Cisco ATAs. Speech is normal in both directions until one of the ATA users presses a Dual Tone Multifrequency (DTMF) digit. At this time, audio is lost in both directions for the call duration.
- Calling between a Cisco ATA and another phone controlled through Cisco CallManager (IP phone or Public Switched Telephone Network (PSTN) user). Speech is normal in both directions until the Cisco ATA user presses a DTMF digit. At this time, one-way audio is experienced (by the non-ATA user) for the entire call duration.
Note: This problem does not occur when Cisco CallManager is not involved in the configuration.
Resolution
The problem occurs when the Cisco ATAs are set to 0x00150015 = Sets both lines to always send DTMF out-of-band. This setting causes one-way voice because there is no way to configure DTMF out of band on Cisco CallManager for H.323 phones.
Changing the AudioMode to 0x00050005 = Sets both lines to always send DTMF inband fixes the problem.