Incoming and Outgoing Calls Through AT0 Trunk Automatically End

Publication Date:  2015-07-24 Views:  270 Downloads:  0
Issue Description
Network: IP phone–U1930–(AT0)–PSTN

Versions:
 U1930: V100R001C01SPC800
 eSpace 7910: V100R001C01SPC500

The calling and called parties of an incoming or outgoing call on an eSpace 7910 IP phone are automatically disconnected after the call is connected for about 3 minutes. The same fault occurs on other eSpace 7910 IP phones.
Handling Process
The VAD function is enabled by default on the U1900 V100R001C01SPC800 to avoid line locking. If no one talks during a call for a period of time (2 minutes by default), the U1900 considers that the peer party has hung up, and releases FXO line resources. Disabling the VAD function can avoid this fault. However, it is recommended not to disable the VAD function. You are advised to prolong the detection period, for example, prolonging it to 5 or 10 minutes.

The command for configuring the VAD function is as follows:

config at0 silence detection switch <on|off> detecttime <1-65535> silencelevelgate <-45~-23>

The following table describes the parameters.



When the default values are used for the three parameters, the U1900 considers that the peer party has hung up if the sound energy on the AT0 line is lower than –45 dB for 120 seconds. As a result, the U1900 releases FXO port resources, and calls end.

To prolong the detection period, for example, to prolong it to 10 minutes, run the following command:
config at0 silence detection switch on detecttime 600


Root Cause
Possible Cause:
The PSTN cannot detect any signals and considers that the call has ended.

Fault Locating:

According to the fault symptom, ask the channel to perform the following test:

1. Make intra-office calls (excluding the AT0 impact). The test result is OK.

2. Directly connect a phone to the AT0 line without using the U1930 and make calls. The test result is OK.

3. After the preceding steps, incoming and outgoing calls through the U1930 still automatically end after they are connected for about 3 minutes. Once in another office, when eSpace 7910 IP phone users make calls to mobile phones through Huawei PBX, sometimes calls cannot be connected. That fault is rectified after the IP phones are upgrade to V100R001C01SPC700. Ask frontline engineers to upgrade the IP phones to V100R001C01SPC700 and test again. The following figure shows the test result.



4. According to frontline engineers, this fault does not occur on the U1930 V100R001C01SPC600. When U1930 is upgraded to V100R001C01SPC800, if no one talks for a period of time during a call, the call automatically ends after about 3 minutes. However, if the calling and called parties talk, the call will not be ended.

5. It is suspected that the voice activity detection (VAD) function is enabled by default for the AT0 trunk on the U1930 V100R001C01SPC800. Log in to the U1930, and run the following command:

show at0 silence detection parameter
The SilenceDetEnable value is 1, indicating that the VAD function is enabled.

6. Run the following command to disable the VAD function:
config at0 silence detection switch off

7. Test again. Calls will not automatically end when no one talks for a long period of time after the calls are connected.



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