... SIP accounts, press 1# key, choose the first SIP to call; press 2# key, choose the second SIP to call...For useful:1, the ... can press 1# key to call; the second SIP Account call to China is cheap, you can press 2# key to call...3, you need ... can press 1# key to call A, then press "Hold" key, then press 2# key to call to B, then press "CONF" key... 1,Protocol support ...