The Difference Between PABX and PBX


Now that VoIP-based PBX solutions are mainstream the question of PBX and PABX and the differences is mainly academic. Still, it is good to know so that you can appreciate the evolution of telephony.


PBX means private branch exchange. In the earlier days of telephony, businesses had a room or a console manned by an operator. The console had dozens of sockets and the operator would plug-in jumpers according to requests by employees to get them an outside line or connect them to another employee in the building. Likewise, incoming calls would be connected to the extension of the called person manually by the operator. The console was the switch operated manually to connect incoming and outgoing calls.


PABX stands for Private Automatic Branch Exchange. The rise of electronic switching led to the demise of the manual switchboard and a small box carried out all functions of employees being able to dial out or carry out intercom conversations. Incoming calls can be switched automatically to the concerned person if the caller knew the extension. The PABX can have embedded software and hardware to work as a public telephone exchange and you can connect routers, modems, and fax machines to the PABX. You could even have an IVR for incoming calls, informing callers to dial a specific number to access a certain department. PABX led to the demise of manual PBX systems.

In both PBX and PABX the system shares one or more PSTN lines with limited internal lines.

The rise of VoIP

The rise of VoIP led to the evolution of SIP phones and the lines between PABX and PBX blur since VoIP PBX or PABX include a host of other facilities and features. It is commonplace to find IP PBX solutions offering

    • Call forwarding
    • Automatic ring back
    • Auto-attendant
    • Call park, call forward, call queue, call transfer
    • Direct inward dialing
    • IVR
    • Ring Groups
    • Speed dialing
    • Voicemail

Modern offices and workers take these features for granted but were it not for VoIP it would not be possible to enjoy these facilities. VoIP PBX or PABX also provides connectivity to standard PSTN landline phones while offering direct voice over internet communications provided by VoIP PBX services provider.

IP PBX solutions may be availed of through a VoIP service provider by using your own in-house solution comprising of SIP phones, routers, and SIP gateway. You can just as well subscribe to hosted service and do away with the need to maintain and upgrade software and hardware. Current solutions are sophisticated, allowing users to make use of standard SIP phones, computer-based softphones, and mobile phones. Further, UC overlaid on IP PBX lets you make use of social media channels, chat, SMS, and video calls as well as conference call facility. With so much available at your fingertips you are not likely to ever go back to the old PBX systems or PSTN.

PSTN is on its way out

As VoIP based IP PBX offers more features and bang for the buck and enterprises discover the benefits of low-cost telephony across international borders with the facility to conference, transfer calls and engage in chat or video calls, the older PSTN lines are becoming redundant and are on the way out. Larger and established enterprises may maintain PSTN connectivity just for the sake of continuity but startups and other businesses may switch over to IP PBX or even use WebRTC based solutions. So, for the present and for the future, there is not much to worry about PBX and PABX and the differences between them. Even the simplest IP PBX can do lots more. With VoIP based IP PBX systems you can change office location and your new IP PBX starts working within a day. If it is a hosted solution you can access services no matter where you are located. With PSTN you would have to surrender existing lines and request a new connection at your new location. The world over PSTN lines is in a state of decline with 2018 seeing a drop of 2 million connections in Brazil, the US, Russia, and China. For the same period, VoIP grew from 338 million to 359 million users whereas PSTN declined from 658 million to 612 million. Even telcos are switching over to IP networks.

Yes, the modern IP PBX is far more versatile. Your business phone works on your mobile through the software and you can use it as if you are on the premises though you may be on the road. Even within the premises the VoIP based PBX can handle hundreds of concurrent calls and become the best communication center for customer service. The VoIP-based PBX is also automatic and now, it is getting a dose of artificial intelligence making it a smart PBX. PBX or PABX, it does not matter in the current context.

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