What is 3CX? A plain-English guide for business owners
3CX explained in plain English: what it is, how it's licensed and hosted, and which businesses it suits.
3CX is a software-based business phone system (a PBX) that runs your calls over the internet instead of an old copper line or a box bolted to the wall. Every staff member gets an extension they can answer from a desk phone, an app, or their mobile — so a small office and a team spread across home and head office both work off the one tidy system.
For most Australian SMEs it replaces an ageing PABX and a pile of separate mobiles with something you can manage yourself — change who rings, record a greeting, or add a starter without booking a technician each time. Here is what 3CX is, how it is licensed and hosted, and who it suits.
What 3CX actually is
3CX is the "brain" of your phones: it connects your extensions to each other and the outside world, and decides what happens on every call — who it rings, what callers hear, where messages land. Because it is software, the same 3CX phone system extension can ring on a desk phone and a mobile at once. Staff use it through:
- The Web Client — calls, chat, presence and settings in a browser, nothing to install.
- The desktop apps (Windows, Mac) and mobile apps (iOS, Android) — so the office number rings on a personal phone without sharing the personal number.
- IP desk phones (Yealink, Fanvil, Snom and others) that 3CX provisions automatically.
How calls get in and out
To reach the outside world, 3CX needs lines — SIP trunks, the internet-delivered replacement for old ISDN and analogue lines (see SIP trunks explained). Your numbers, including 1300 and 1800 numbers, sit on that trunk and can usually be ported across. Once calls arrive, 3CX routes them with a few core tools:
Inbound Rules
route each incoming number (DID) to the right place; Outbound Rules decide which trunk and caller ID to use when dialling out.
Ring Groups
ring a set of people together, while Call Queues hold callers in line and distribute them by a strategy — Hunt/Ring all, Round robin, Least talk time or Longest waiting.
A Digital Receptionist (IVR / auto-attendant) answers with a "press 1 for sales" menu, and Office Hours route after-hours calls differently.
How 3CX is licensed
3CX is licensed by the number of simultaneous calls you need, not by headcount — a licence for eight concurrent calls supports a much larger team, since not everyone is on the phone at once. Higher feature tiers unlock things like Call Queues, Call Recording and deeper CRM integration.
Too small and you get busy tones at peak; too large and you overpay. See 3CX licensing explained, or we can size it against your real call volumes through a free bill review.
Where 3CX is hosted
The software has to run somewhere — three broad choices:
Hosted / cloud
— it runs in a data centre with no hardware on site, and updates and backups are handled for you. Where most SMEs land; see hosted PBX.
Self-hosted
— you run it on your own cloud account or virtual machine, for more control.
On-premise
— it lives on a server in your building, suiting specific compliance needs.
Each trades off cost, control and maintenance — our hosting options guide covers which fits which business.
Managing it day to day
Everything is configured through the web-based Admin Console: add Extensions, set up routing, record greetings, manage Voicemail and voicemail-to-email, schedule Backup & Restore, and control security. It connects to Microsoft Teams so staff can call from within Teams, plus Microsoft 365 and common CRMs that pop and log the customer record automatically. The Call Flow Designer (CFD) handles advanced logic without a developer.
A word of honesty: the day-to-day is manageable in-house, but the first build — trunks, NAT, the Session Border Controller (SBC), STUN and the anti-fraud limits that guard against toll fraud — is where most businesses want a hand. That groundwork keeps audio clean and the bill free of surprises.
Which businesses 3CX suits
3CX is a strong fit if you:
- Are replacing an old PABX or moving off Telstra DOT and want to keep your numbers.
- Have staff across multiple sites, home offices or on the road.
- Want to manage greetings, hours and routing yourself instead of paying per change.
- Already use Microsoft 365 or Teams and want calling joined up with it.
It leans on good internet, so a sound connection — ideally with failover — matters. If you would rather not run the setup, SIP Connect installs and supports 3CX across Melbourne; reach us on 1300 747 266 or our contact page.
What we see installing this in Melbourne
Most Melbourne SMEs we move onto 3CX are coming off a Telstra DOT setup or an old on-prem PABX, and the part that catches people out is rarely 3CX itself — it is the connection underneath. Cheap NBN plans with 20Mbps upload look fine on paper but choke once eight or ten concurrent calls land at lunchtime. We always test on the actual office connection, with the office router, before we sign off.
The other common trip-up is a consumer-grade router with SIP ALG quietly turned on, mangling registrations and dropping one-way audio a week after cutover. We disable it as a matter of course. Number porting from Telstra usually runs 10-15 business days and we plan cutovers for a Tuesday or Wednesday morning so any oddities can be sorted same week, not over a weekend.
Where we earn our keep is the handholding after go-live: walking reception through the Web Client, getting mobile apps onto staff phones without flattening batteries, and tuning call recording so it sits inside the obligations under the Telecommunications Act.
Frequently asked questions
Do I need to buy new phones to use 3CX?
Not necessarily. Many existing IP desk phones can be re-provisioned for 3CX, and plenty of teams skip desk phones and use the Web Client or the apps. We can check whether your handsets are compatible first.
Can I keep my existing phone numbers?
Yes. In almost all cases your landline, 1300 or 1800 numbers can be ported to 3CX, with a planned cutover so there is no gap where customers can't reach you — see porting numbers to 3CX.
Is 3CX the same as VoIP?
Related but not identical. VoIP means carrying calls over the internet; 3CX is the phone system that manages those calls, using VoIP via SIP trunks to reach the outside world.
What internet do I need to run 3CX well?
A stable connection with enough upload capacity for your busiest call period — business NBN, fibre or 5G all work. For phone-dependent businesses we recommend a second link for failover so calls keep flowing if the primary drops.
Get a free bill analysis — and stop overpaying
Send us a recent phone or internet bill. We’ll show you exactly where the waste is — our bill reviews have identified savings of up to 65%.