S300 - is a PBX of VoIP technology. It has all the functionality that a telephone exchange can have.

IP phones: 300 (expandable up to 500)
Simultaneous conversations: 60 (expandable to 120)
Number of trunks: 100
Analog Ports (FXS/FXO/BRI): 24
Wireless channels (GSM/3G/4G): 6
Digital ports (E1/T1/PRI): 3