1.Caller ID for C.O Lines and extension,telephone number is not lost when transferring . 2.Outline calling on duty manual/automatic mode,Ringtone mode. 3.Three-section of digital recording can be 20 seconds .¡ê¡§optional 30s-90s). 4.When calling no one answer or the line is busy can be transferred . 5.Calling level for extension and the talking time is limited . 6.The extension number ranges can be mixed . 7.Outline or inline calls can be answered the Phone for Others , transfer, retention, monitor . 8.Checking telephone caller id number and voice checking . 9.Automatic IP dial-up . 10.Call center function, extension hotline number, Ringtone function. 11.Automatic on duty and abbreviated dialling . 12.Remote maintenance, hardware self-tested .