1,2 line SIP phone 2,Support 2 SIP Aaccount 3, Support Transfer ... /Three-way conference/Call waiting fun Important: It can store two SIP accounts, press 1# key, choose the first SIP to ... choose the second SIP Account to call...2, the two SIP Account from two ITSP, the first SIP Account call to USA ... -free in a semiduplex way to ensure the talking quality; Two Line VoIP Phone