Quick answer: What is VoIP?
VoIP (Voice over Internet Protocol) is technology that converts your voice into digital data packets and transmits them over the internet, just like an email or a video stream. Instead of a traditional phone line, calls travel through your broadband connection. For businesses, this means lower call costs, more flexibility, and phone features — like auto attendants, call recording, and mobile apps — that old copper-wire systems simply cannot provide.
What is VoIP? (Voice over Internet Protocol Explained)
Definition: Voice over Internet Protocol (VoIP)
Technology that digitises voice audio and transmits it as data packets over an internet connection, rather than through a traditional analogue or ISDN telephone line. VoIP enables phone calls to be made from computers, smartphones, IP desk phones, or any internet-connected device.
Every time you make a call on WhatsApp, Zoom, or Microsoft Teams, you’re already using VoIP. Business VoIP systems like 3CX do the same thing — but with a full professional phone system on top: extension numbers, call queues, IVR menus, call recording, and direct phone numbers that ring on any device.
How does VoIP work, technically?
When you speak into a VoIP phone or app, this is what happens in real time:
- Your voice is captured by the phone’s microphone and digitised — converted from an analogue sound wave into a stream of digital data.
- The data is compressed using a codec (commonly G.711 or G.729 for business VoIP). The codec trades off audio quality against bandwidth usage.
- The compressed audio is broken into small data packets, each labelled with destination information — just like any data travelling over the internet.
- The packets travel over your internet connection (broadband, fibre, 4G/5G) to the recipient’s VoIP system or phone.
- At the other end, the packets are reassembled in order, decoded, and converted back into analogue audio through the speaker.
- This entire process happens in milliseconds — imperceptible to the caller when the network quality is good.
What is a VoIP codec?
A codec (coder-decoder) is the algorithm that compresses your voice for transmission and decompresses it at the other end. The two most common in business VoIP:
- G.711: Uncompressed, highest quality, uses ~64 kbps per call. Best on fibre or high-speed NBN.
- G.729: Compressed, slightly lower quality, uses only ~8 kbps per call. Ideal for limited bandwidth or many simultaneous calls.
3CX supports both automatically, selecting the best option based on your connection.
VoIP vs Traditional Phone Lines — What’s the Actual Difference?
Australian businesses are still running a mix of traditional PSTN (copper), ISDN, and VoIP systems. Here’s an honest comparison:
| Traditional (PSTN/ISDN) | VoIP | |
|---|---|---|
| Call transmission | Copper phone line | Internet connection |
| Setup cost | High — physical line installation | Low — uses existing internet |
| Monthly cost | Per-line rental + call rates | SIP trunk subscription, low call rates |
| International calls | Expensive | Near-free (data only) |
| Scales easily? | No — each line needs a physical connection | Yes — add users in minutes |
| Features | Basic — call waiting, voicemail | Advanced — IVR, call recording, CRM, AI |
| Works on mobile? | No | Yes — full softphone app |
| Remote work support | No | Yes — works anywhere with internet |
| ISDN switch-off risk | Yes — Telstra ending ISDN | No — future-proof |
⚠️ Australia’s ISDN Switch-Off
Telstra has been progressively decommissioning ISDN lines across Australia. If your business still relies on ISDN, migrating to VoIP is not optional — it’s a matter of when, not if. VoIP over SIP trunking is the direct replacement.
What Are the Business Benefits of VoIP?
1. Significantly lower call costs
Traditional phone lines charge per minute for calls — especially interstate and international. VoIP calls travel as data over your existing internet connection. SIP trunking typically reduces a business’s monthly phone bill by 40–70% compared to ISDN or PSTN lines.
2. Work from anywhere — truly
The 3CX softphone app on a laptop or mobile works exactly like a desk phone — same extension number, same call quality, same features. A remote worker in Melbourne answers calls from your Sydney office number. Staff travelling internationally use the app over Wi-Fi at zero additional call cost. For hybrid teams, this isn’t a workaround — it’s the native experience. See how it works with 3CX’s phone system.
3. Scale up (or down) without calling a technician
Adding a new employee to a traditional phone system means calling a technician to run a physical line. Adding a new VoIP extension takes two minutes in the admin console. Likewise, scaling down — seasonal businesses, economic downturns — means simply deactivating extensions, with no contracts tied to physical infrastructure.
4. Advanced call features included
Features that cost thousands to add to a traditional PBX are standard in modern VoIP systems:
- IVR / Auto Attendant — professional call menus (‘Press 1 for sales, 2 for support’)
- AI Voice Assistant — handles calls automatically when staff are unavailable
- Call recording — for compliance, training, and dispute resolution
- Call queues, hold music, callbacks
- CRM integration — calls logged automatically in HubSpot, Salesforce, and others
- 1300 and 1800 numbers — route to any VoIP extension, anywhere in Australia
5. Business continuity built in
Traditional phone lines are physically fixed. A fire, flood, or office move means no phones. VoIP extensions exist in software — redirect all calls to mobile in seconds. Staff can work from home without any reconfiguration.
6. One system across multiple locations
A business with offices in Sydney, Brisbane, and Perth can run a single 3CX phone system across all sites. Internal calls between sites are free. A call to the Sydney number can be transferred seamlessly to a Brisbane extension.
What Does VoIP Require to Work Properly?
Internet speed
Each active VoIP call uses approximately 80–100 kbps (with G.711 codec) or as little as 20 kbps (G.729). For a business expecting 10 simultaneous calls, you need at least 1–2 Mbps dedicated to VoIP. The more important factor is latency and packet loss, not raw speed.
| Metric | Acceptable | Problematic |
|---|---|---|
| Latency (ping) | Under 150ms | Over 200ms |
| Packet loss | Under 1% | Over 3% |
| Jitter | Under 30ms | Over 50ms |
| Upload speed (10 calls) | 1–2 Mbps | Under 500 kbps |
Router and firewall configuration
- QoS (Quality of Service): Prioritise VoIP packets over general internet traffic on your router. This prevents call quality dropping when someone else is downloading large files.
- ALG disabled: Application Layer Gateway (ALG) on routers often causes connection issues with modern SIP systems. Disable SIP ALG on your router. See our ALG guide for details.
- Firewall ports: SIP (port 5060 UDP/TCP) and RTP media (ports 9000–10999) must be open. Run the 3CX Firewall Checker to verify your setup.
Types of VoIP for Business
1. Cloud-hosted VoIP
The VoIP phone system (PBX) runs on servers in the cloud — managed by your provider. Your business just needs IP phones or softphone apps and an internet connection. 3CX hosted is an example. Low upfront cost, no servers to maintain, automatic updates. Best for most SMEs.
2. On-premises VoIP (IP PBX)
The VoIP PBX hardware sits in your server room or comms cabinet. You own and manage the system. Higher upfront cost, more control, better for businesses with strict data residency requirements or complex custom configurations. 3CX can also be deployed on-premises.
3. SIP Trunking (for existing PBX systems)
If you already have a PBX system, SIP trunking lets you connect it to the internet for outbound and inbound calls — replacing your ISDN or PSTN lines without replacing the whole phone system. This is often the most cost-effective migration path for established businesses.
VoIP Phone Equipment — What Do You Actually Need?
| Option | What it is | Best for |
|---|---|---|
| IP desk phone | Hardware phone that connects directly to your network (e.g. Yealink, Snom, Fanvil) | Reception desks, heavy phone users, executive setups |
| Softphone app | App on laptop or PC that acts as a phone (3CX desktop app) | Office staff, hybrid workers |
| Mobile app | 3CX app on iPhone or Android | Field staff, remote workers, travelling executives |
| ATA adapter | Device that connects your existing analogue phone to VoIP | Keeping old handsets during transition |
| Conference phone | IP-based speakerphone for meeting rooms (e.g. Yealink CP960) | Meeting rooms, boardrooms |
Frequently Asked Questions
What does VoIP stand for?
VoIP stands for Voice over Internet Protocol. It refers to the technology that transmits voice calls as data packets over an internet connection, rather than through a traditional telephone network.
Is VoIP reliable enough for business use?
Yes, when deployed on a business-grade internet connection with QoS configured. Enterprise-grade VoIP systems like 3CX are used by thousands of Australian businesses including medical practices, law firms, financial services companies, and multi-site retailers.
Can I keep my existing phone number when switching to VoIP?
Yes. Number porting allows you to transfer your existing business phone number to your VoIP provider. Geographic numbers (02, 03, 07, 08), mobile numbers, 1300, and 1800 numbers can all be ported. Aatrox Communications manages number porting as part of our 3CX setup service.
What is the difference between VoIP and a SIP phone?
VoIP is the broad technology category — sending voice over the internet. SIP (Session Initiation Protocol) is the specific protocol most VoIP systems use to manage call setup and routing. A ‘SIP phone’ is a phone that uses the SIP protocol to make VoIP calls. SIP trunking is the service that connects your VoIP PBX to the public phone network.
How does VoIP compare to ISDN in Australia?
ISDN is a legacy Telstra product that uses digital signals over copper phone lines. It is far more expensive than VoIP and lacks modern features. Crucially, Telstra is decommissioning ISDN across Australia — making migration to VoIP via SIP trunking the only long-term option.
Does VoIP work with a 4G or 5G connection?
Yes. 3CX works over 4G and 5G connections via the mobile app or with a 4G/5G router providing connectivity for desk phones. Modern 4G and 5G networks provide more than adequate quality for business calls.
What happens to VoIP calls during a power outage?
IP phones and your router need power. During a power outage, VoIP phones will stop working unless on UPS backup. However, VoIP systems can automatically redirect all calls to mobile numbers during an outage — something traditional fixed lines cannot do.
Is VoIP suitable for small businesses with only 2–5 staff?
Absolutely. 3CX’s free tier supports up to 10 simultaneous calls with full features at no ongoing licence cost. Small businesses get enterprise-grade telephony at a fraction of the traditional cost.
Ready to switch your business to VoIP?
Aatrox Communications are Australian 3CX VoIP specialists who design, install, and manage VoIP phone systems for businesses across Australia. We handle everything from number porting and hardware supply to ongoing support.