i'm using my own local SIP Server (3CX Phone System v3.0.2328.0 free edition), i have no SIP account on any SIP Provider, i have no WAN connection. I'm using a Grandstream GXW4104 (FXO gateway), 2 units of BT101 and a unit of BT200 as my IPPhones. I connected one PSTN line to the GXW4104. local exchange is fine.. incoming PSTN call is also fine but when i try to transfer it to another extension.... my voice can be heard on the caller side (outside PSTN caller), but i couldn't hear anything on the IPPhone side (extension where the call was transfered). Another problem is i couldn't make a call from my IPPhones going to outside PSTN phones..., i always got a busy tone when i make a VoIP to PSTN call... i have completely followed the instruction on how to configure the GXW4104 with 3CX, as well as the BT101 and BT200.. pls help me on this... :?: help me figure out whats wrong and what could be the cause of the problem..