Extension call Delay Problem

Hi, I’m Newbie.

I have install Asterisk, and use TDM400, its work fine when i call any extension from hard phone. I just add a SIP Phone but when i call from SIP Phone to any extension its wait almost 5 seconds before start dialing.
Please help me out is it any configuration issue or its SIP Phone problem.
but when i call from hard phone (extension of TDM400) to SIP Phone its ring immediately.

SIP Phone = Teledex IP250D.

Thankz in Advance