When a user perform calls from the U1900 to the IAD 1224. The IAD has a long time before it rings, if the user pick up the phone before it rings the call can be established (without any previous ring) So if someone take the phone and try to do an outgoing call he will pick up the incoming call, and will not listen the dial tone so he can dial any number.
This means that the incoming call is directly connected without any ring and the call will be established with the first user who pickup the phone.
It takes 1 second or more to ring.
This happens with any user, sip or pots user
1. Collect IAD diagnose information under Diagnose:
2. Capture network package at IAD side, include two scenarios: one is pick up before it ring, another is pick up after ring, and record the caller/called/IP/call time.
For this issue, customer configured region as Brazil, when the region is Brazil, it will display caller ID first via DTMF, then start to ringing, each digit will takes 160ms,
Customer called number is 3 digit, so totally will take around 500ms.
Solution: change region to US
In this version, only mainland China, HongKong, Russia, and Brazil have default FXO busy tone values. Other countries' FXO busy tone parameters are set to the default vaule of mainland China.