The SIP IP PBX is a feature rich SIP IP PBX offering PBX service and VoIP Telephony management in one device. There are many features about SIP IP PBX here.

Advanced telephony Management and feature Rich IP PBX solution
Supports 50 extensions
150 Vocemail accounts
20 Concurrent calls
Feature for online interactivity
Features a Web-Calling
Provides a VPN Server for Secured connectivity
Built-in FXO and FXS ports for PSTN connection
Supports ITU-T G. 711a/u; GSM/MS-GSM; G. 729A/B; VAD and CNC speech Codec
Features a powerful interactive voice response
Feature and voice Message
Recording Features a built-in SIP proxy register server
Provides Call Detail Record
Easy configuration via Web browser.