Abnormal Ringing of ET523 When an AT0 Trunk User Calls the SoftCo

Publication Date:  2015-07-16 Views:  94 Downloads:  0
Issue Description
Version: SoftCo V100R002C03

Networking: The ET523 (a phone) connects to the SoftCo9500. The SoftCo9500connects to the carrier's network through the AT0 trunk.

Fault symptom: The ET523 rings abnormally and all the four line indicators are red. When a user picks up any lines, this user hears the busy tone.
Handling Process
Step 1 Make a frequency shift keying (FSK) recoding. According to the FSK recording, the volume of the hang-up signal sent by the trunk is so small that the SoftCo does not detect the hang-up of the calling party. As a result, the called party's phone keeps ringing.

Step 2 Run the config modify at0tkc slot <2-9> portinboard <list(0-7)> [fskgain <0-20>] command to increase the SoftCo FSK gain. Then, the fault is resolved.

Note:
You are advised to increase the FSK gain incrementally. There is no fixed value because the value of the FSK gain is affected by the level of signals sent from the peer device.

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Root Cause
An outer-office user calls an intra-office user through the AT0 trunk. Before the intra-office picks up the phone, the outer-office user hangs up the phone. However, the SoftCo does not identify the phone hang-up. As a result, the intra-office user's phone still rings.

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