i'm sorry for my bad english ! Hi i have configured 3cx rel 6.1.0 and a gatway gsm Portech MV-372 with firmware v6.694.d. I haven't problem to make and recive calls trought this gatway, but when i call a busy or inexistent destination i can't understand that this destination it's busy or inexistent... because i hear a normally free tone and not busy tone or other. I suppose that this can correct by a right combination of options in the section Sip settings-->Sip Responses of portech. This section espose the sequent options 1] Response on prt busy : 1.1) 486 Busy here 1.2) 503 Service unavailable 2] SIP Responses 2.1) 180 Ringing ( Auto force to ON, if 183 was OFF. ) (this is checkbox that assume the on or Off values) 2.2) 183 Session Progress (this is checkbox that assume the on or Off values) i have test all of combinations but i haven't find the soultion. Another problem it's that the 3cx try use for first the gsm gatway and because this can't make the call use the voip provider(gateway) for the same call. result 3cx try to call destination 2 times 1 with portech and then with voip provider (gateway). Thank you for all help.