1.1/2 phone line 2.SIP V2.0, MGCP V1.0(option) protocols 3.T38 fax 4.Compatible with the mainstream in the softswitch 1/2FXS/4FXS/4FXO,8FXS/8FXO,16FXS/16FXO multiple interfacesStandard SIP V2.0, MGCP V1.0 protocolsStandard G.711A/U,G.723.1,G.729A/B,G.168,PCM A/U codeCall forwarding, Call hold, Caller ID, DND standard voice serviceBusy tone, Power-down protection , Fault identificationMany users ...