Plus PBX  | SMB PBX  | MS PBX  | Enterprise Soft Switch Server | |
Extension limit | 60 | 300 | 1000 | 20000 |
PSTN (FXO) ports | 2 | 4 | NO (need FXO Gateway) | NO (need FXO Gateway) |
FXS ports | No (need ATA) | 1 | No (need ATA) | No (need ATA) |
SIP Trunks | Up to 16 | Up to 50 | Up to 300 | Unlimited |
Concurrent calls | 15 | 100 The number of concurrent external calls depends on the channels provided by the ISP. | 300 The number of concurrent external calls depends on the channels provided by the ISP. | Unlimited (depends on server specs) The number of concurrent external calls depends on the channels provided by the ISP. |
Call Recording |  USB and SD card supports | SD card supports up to 256GB | Internal Hardisk needs to be installed up to 4TB | Support any storage depending on server hardware hard-installed |
IVR | | | | |
Support XonTel Call center |  | | | |
VOIP protocols | SIP | SIP and IAX | SIP and IAX | SIP and IAX |
Network ports (LAN,WAN) | 10/100 Mbps | 10/100 Mbps | 1 Gbps | Up to 10 Gbps |
Firewall | | | | |
Transport Protocols | UDP, TCP, TLS | UDP, TCP, TLS | UDP, TCP, TLS, WSS | UDP, TCP, TLS, WSS |