I have 1 polycom model is vtx 1000 analog conference station connected to UC520 FSX port. The conference station can make 1 to 1 call without any problem but it can't conference for 3 party if the conference initial by conference station. Once I press the conf buttom on conference station I can see flash then it can't get second line. In my CME i already specify dual line for the ephone-DN that assign to conference station. If the conference call not initial by conference station, let say I use my mobile phone call the conference station once pick up, I press conference buttom on conference station then I can get the second line and get 1 more party join the conference. However it it support max 3 party conference.

My question:

1. Does the analog conference work on this way?

2. Is there any wrong in my configuration that cause conference station can initial conference call?

3. What to configure so I can let my conference station get the second line?

Regards,