Glossary
PBX
A Private Branch Exchange is the phone system itself: the thing that knows extension 204 belongs to accounting, rings it when someone presses 2, and sends the call to voicemail when nobody answers.
A PBX, or Private Branch Exchange, is the telephone switch that a business uses to connect internal extensions to each other and to outside lines. It provides features such as extensions, transfers, voicemail, menus, ring groups and call queues. A PBX can be a physical unit installed on site, software running on a company server, or a hosted service run by a provider, usually called a cloud PBX.
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What it means
Before PBX systems, every desk that needed a phone needed its own outside line. A PBX lets a business share a smaller number of outside lines among many internal extensions and adds the features people expect from an office phone: dial a colleague by extension, transfer a call, put someone on hold, leave voicemail, reach a department through a menu.
The term now covers three very different things. A traditional PBX is a cabinet in a phone closet with physical line cards. An IP PBX is software or an appliance that does the same job over the network using SIP. A cloud PBX is the same software run by a provider and delivered as a service, so the business owns no switch at all.
How it is used in a business phone system
- The PBX holds the directory: which extension is which person, which group answers sales, and which voicemail box belongs to whom.
- It runs the call flow: the main menu, business-hours rules, ring groups, queues and fallbacks.
- It connects to the outside world through phone lines, or, for an IP PBX, through a SIP trunk.
- Whoever owns the PBX is responsible for maintaining it, which is the main practical difference between on-premises and hosted.
How 3CTel uses it
3CTel's business phone system is a hosted PBX. Extensions, menus, ring groups, queues, voicemail and recording are configured in the hosted system and delivered to desk phones and apps over the internet, so there is nothing to install or maintain on site. Businesses that already own an IP PBX and want to keep it can connect it to 3CTel with SIP trunking and carry on using their existing setup.
Business Phone
Reliable calling with routing your team will actually use.
Learn more: Business PhoneHosted PBX
The PBX as a service: endpoints, extensions, dial plans, failover and admin.
Learn more: Hosted PBXSIP Trunking
Carrier-grade SIP trunks for the PBX you already run — channels, DIDs and failover sized to your traffic.
Learn more: SIP TrunkingCommon questions about PBX systems
Do I still need a PBX if I use a cloud phone system?
You use one, but you do not own one. A cloud phone system is a PBX operated by the provider and shared securely across customers. Your extensions, menus and rules live in that hosted PBX, and your desk phones and apps connect to it over the internet. There is no cabinet, server or line card at your premises.
What happens to my existing PBX if I switch providers?
You have two options. Retire it and move extensions to a hosted PBX, which removes the maintenance burden. Or keep it and replace only the outside lines with a SIP trunk from the new provider, which preserves your investment and your configuration. The right choice depends on the age of the system and what it still does well.
Related pages.
Business Phone
Reliable calling with routing your team will actually use.
Learn more: Business PhoneSIP Trunking
Carrier-grade SIP trunks for the PBX you already run — channels, DIDs and failover sized to your traffic.
Learn more: SIP TrunkingCloud PBX vs traditional PBX
Own the switch or rent it: ownership, maintenance, remote users and the path between them.
Learn more: Cloud PBX vs traditional PBXFrequently asked questions.
In everyday use, yes. 'Phone system' usually means the PBX plus the phones connected to it. Technically the PBX is the switch and the phones are endpoints.
Enough for the maximum number of simultaneous outside calls. With a SIP trunk that number is a setting rather than physical wiring, and can be adjusted as call volume changes.
Not sure which of these you need?
Describe how your calls arrive today and a 3CTel specialist will map them to the right pieces, build them on a temporary number and quote the result before anything is billed.