What Is VOIP? Plain English Guide for Australian Business

VOIP (Voice over Internet Protocol) is a technology that lets you make phone calls over your internet connection instead of a traditional copper phone line. This guide explains what VOIP actually is, how it works in plain English, and what it means for your business phone setup. We cover the different types of VOIP services, common misconceptions, and the practical steps for getting started. If you have an NBN connection in Australia, you are almost certainly already using VOIP whether you know it or not.

What VOIP Actually Is (No Jargon)

VOIP stands for Voice over Internet Protocol. That is the technical name for making phone calls over the internet instead of over a copper phone line.

Here is how it works at a basic level. When you speak into a phone, your voice is converted into tiny packets of data, the same way an email or web page is broken into packets. Those packets travel over your internet connection to the other person, where they are reassembled into audio. The whole process happens in milliseconds and, on a decent connection, sounds identical to a traditional call.

The old way of making calls used the PSTN, which stands for Public Switched Telephone Network. That is the copper wire phone network that Telstra built across Australia over decades. Calls travelled as electrical signals through copper cables. That network is now switched off. Australia completed the PSTN shutdown in 2022. Every phone call in Australia now runs over digital infrastructure, including VOIP over NBN.

How VOIP Is Different From Your Current Setup

When NBN was rolled out, ISPs quietly moved their customers from PSTN landlines to VOIP. Most customers had no idea this happened. Your ISP modem almost certainly has a green phone port on the back. That port connects to an ATA, which stands for Analog Telephone Adapter.

An ATA takes the analogue signal from your old cordless handset and converts it to digital data that travels over NBN. The VOIP service is programmed into the modem firmware. You do not own the service, the credentials, or the configuration. Your ISP controls it entirely.

This matters because the ISP ATA setup gives you almost nothing in terms of business features. You get one line. If two customers call at the same time, the second gets an engaged tone. There is no hold music, no voicemail-to-email, no after-hours message, no auto-attendant. It is the bare minimum VOIP wrapped in familiar packaging.

A proper business VOIP service is different. You sign up with a VOIP provider, get your own SIP credentials, connect a PBX (either hosted in the cloud or on your own hardware), and get a full-featured phone system. You own the service. You can port your number. You can configure everything from call routing to hold music to after-hours messages.

What VOIP Means for Your Business Practically

Switching to a proper VOIP phone system changes what your business phone can do. Here is what becomes available that you almost certainly do not have on a basic ISP setup.

• Multiple simultaneous calls. Multiple staff can take calls at the same time on the same phone number. No more engaged tones.
• Hold music. Put a caller on hold without them hearing dead air. Reduces hangups.
• Auto-attendant. Greet callers professionally and route them. "Press 1 for sales, 2 for accounts."
• Voicemail to email. Voicemails arrive as audio attachments in your inbox. No missed messages.
• After-hours routing. Calls outside business hours go to a recorded message or an on-call mobile.
• Call recording. Record calls for training, compliance, or dispute resolution.
• Softphones. Take work calls on your mobile or laptop using an app. No desk phone required.
• Ring groups and hunt groups. Route incoming calls to the right team or individual.
• 1300 and 1800 numbers. Present a national number to callers while calls route to any Australian location.

Most of these features come standard with entry-level hosted VOIP plans. You do not need enterprise infrastructure to access them. A 2-person business can have the same call handling capability as a 200-person business.

The Different Types of VOIP Setups

Not all VOIP setups are the same. There are four main types, each suited to different business sizes and needs.

1. Hosted (Cloud) PBX

This is the most common setup for Australian SMBs. Your PBX (the system that manages calls) runs on servers operated by a VOIP provider. You do not buy or maintain any phone system hardware on your premises. You pay a monthly subscription per user. The provider handles upgrades, maintenance, and reliability.

Best for: 1-50 seat businesses that want a full-featured phone system without IT infrastructure overhead. Minimal upfront cost. Scales easily as you grow or shrink.

2. On-Premise PBX

You buy and install a PBX server on your premises. Popular options include 3CX (software-based, runs on a small Windows or Linux server) and Asterisk (open-source). You or your IT provider manages the hardware and software.

Best for: businesses with 20+ seats, strong in-house IT capability, or specific compliance requirements that mean data cannot leave the premises. Higher upfront cost but lower per-user ongoing fees at scale.

3. ATA Adapter (Basic VOIP)

An ATA adapter lets you connect an old analogue handset to a VOIP service. This is what your ISP does with the green port on your modem. You can also buy a standalone ATA from brands like Grandstream and connect it to your own VOIP service, giving you proper SIP credentials and control, while keeping your existing analogue handsets.

Best for: sole traders or very small offices that want basic VOIP without switching handsets. Limited features compared to a full hosted PBX.

4. SIP Trunks

A SIP trunk is a VOIP connection that attaches directly to an existing PBX, either on-premise or hosted. Instead of physical phone lines, SIP trunks are virtual lines that carry calls over your internet connection. Larger businesses use SIP trunks to connect their PBX to the public phone network at a lower cost than traditional ISDN lines.

Best for: businesses that already have a PBX and want to replace expensive ISDN or analogue lines with cheaper VOIP calling. Not relevant if you are starting fresh with a hosted PBX.

VOIP vs Traditional Landline: A Direct Comparison

Common Misconceptions About VOIP

"VOIP call quality is bad"

This was true ten years ago. It is not true anymore on a modern NBN connection. VOIP calls on a stable connection with low jitter sound indistinguishable from traditional calls. The issue is not VOIP itself, it is connection quality. VOIP calls use very little bandwidth (around 85-100 Kbps per simultaneous call) but are sensitive to jitter and packet loss. If your internet connection has consistent, low-jitter performance, your calls will sound great.

If you are on a poor FTTC or FTTN NBN connection with variable upload speeds, call quality can suffer. The fix is either a better NBN tier, a router with QoS (Quality of Service) settings that prioritise voice traffic, or switching to a more stable NBN technology like FTTP or HFC.

"Setting up VOIP is complicated"

A hosted PBX setup is genuinely straightforward for most small businesses. A good VOIP provider walks you through the whole process. You provide your number, your internet details, and your call routing preferences. They configure everything. Many providers can have a small business running on a new phone system in a day or two.

The complication people imagine, server rooms, IT contractors, complex hardware, applies to on-premise PBX deployments. Hosted VOIP removes all of that. There is nothing to install on your premises except a desk phone or a softphone app.

"I'll lose my phone number if I switch"

Number porting lets you keep your existing phone number when you switch providers. Your number belongs to you, not to Telstra or your ISP. The porting process is governed by ACMA (Australian Communications and Media Authority) rules. It typically takes 5-10 business days for standard geographic numbers (02, 03, 07, 08 prefixes) and can take longer for mobile and 13/1300/1800 numbers.

There is a brief period where calls may fail during the port transfer, usually measured in minutes. A competent VOIP provider manages this process and advises you on how to handle the transition.

"VOIP is more expensive than what I have"

For most businesses, a proper VOIP phone system costs less than an equivalent traditional setup. Entry-level hosted VOIP plans in Australia start around $15-25 AUD per user per month with unlimited local and national calls included. There are no call charges for most plan types. Compare that to a traditional business phone line bundle plus per-call charges plus the cost of features that are now standard in VOIP.

"What happens in a power outage?"

This is a legitimate concern, not a misconception. VOIP relies on your internet connection, and your NBN modem and router need power to work. If the power goes out, VOIP calls stop working unless you have battery backup (a UPS, or Uninterruptible Power Supply) for your modem and router.

A UPS costs around $80-200 AUD and provides 30-60 minutes of runtime for a modem and router. For businesses where continuous phone availability during outages is critical, this is a worthwhile investment. Many VOIP providers also support call failover to a mobile number if your internet drops, so inbound calls keep working even when your office internet is down.

Is VOIP Right for Every Business?

For the vast majority of Australian businesses, yes. VOIP is the right choice and, given the PSTN shutdown, effectively the only choice. But there are a small number of edge cases where you need to plan carefully.

When to think carefully before switching

• Rural areas with unreliable NBN. If your business is on a fixed wireless or satellite NBN connection with variable latency, call quality can be inconsistent. Test your connection quality first. Some rural businesses rely on 4G/5G mobile data as a backup or primary internet connection, and VOIP works on 4G/5G if the signal is strong.
• Fire alarm and lift panels. Traditional fire alarm systems, lift emergency intercoms, and some EFTPOS terminals and alarm monitoring services were designed for analogue phone lines. These may not work on VOIP without adaptation. You need to check with your installer or provider before cutting over. Some hospitals and care facilities have specific requirements that need careful planning.
• Fax machines. Standard fax does not work reliably on VOIP. The solution is either a virtual fax service (fax-to-email) or a dedicated fax ATA adapter. Most businesses that still need fax capability have already moved to fax-to-email.
• Medical and emergency services with 000 requirements. VOIP supports 000 emergency calling but requires your service address to be correctly registered with your provider. For businesses where 000 reliability is absolutely critical, confirm the setup with your provider before going live.

What Most Businesses Get Wrong About VOIP

After watching businesses navigate the switch to VOIP, the same mistakes come up repeatedly. Here are the three that cause the most friction.

Mistake 1: Starting with the phone instead of the service

The most common mistake is buying a VOIP desk phone before choosing a VOIP provider. A VOIP handset like a Yealink T31P connects via Ethernet to a VOIP service, not via the green port on your modem. If you buy the handset first, you have hardware with nowhere to plug it in and no service to connect to.

The correct order is: choose a VOIP provider, set up your service, then connect your phones. The provider will often supply compatible handsets or pre-configure them for you. Start with the service, not the hardware.

Mistake 2: Thinking you are already on a "proper" VOIP service

Many business owners think their NBN phone is a VOIP service. It is, technically, but it is the most basic possible version. Your ISP ATA gives you one line. You do not own the SIP credentials. You cannot configure the service. You have none of the business features described above.

If you are plugging a cordless handset into the green port on your NBN modem, you are on an ISP-controlled ATA, not a business VOIP service. Calling your ISP and asking for your "SIP credentials" will almost certainly result in a confused support agent who does not know what you are asking for. They will not be able to give you access to configure the service yourself.

Mistake 3: Choosing the cheapest plan without checking call quality requirements

Not all VOIP providers offer the same call quality infrastructure. The cheapest option may route calls through overseas infrastructure with higher latency, or may not support Australian number porting, or may not have local AU support when something goes wrong. Check that your provider has AU-based call infrastructure, can port your existing number, and has a support team that understands the Australian market.

Australian Businesses: What You Need to Know

VOIP in Australia has some specific realities that do not apply everywhere else. Here is what matters most for Australian SMBs.

The PSTN shutdown is done

Australia completed the rollout of NBN and the shutdown of the copper PSTN network. This means every phone call in Australia now runs over digital infrastructure. You are not choosing whether to use VOIP. You are already using it. The question is whether you use a basic ISP-supplied ATA or a proper business VOIP service with full features and portability.

NBN connection type affects call quality

VOIP call quality depends on the consistency of your internet connection more than the raw speed. A 25 Mbps FTTP connection with stable latency sounds better than a 100 Mbps FTTN connection with variable jitter. Check your NBN connection type. FTTP and HFC connections generally deliver the most consistent performance for VOIP. FTTN and FTTC can vary depending on line length and node congestion. Fixed wireless can be inconsistent in some areas.

You can test your connection's VOIP readiness with the NTKComms VOIP Bandwidth Calculator, which assesses your NBN connection type and simulates call quality under different loads.

Number porting in Australia

Australian number portability is governed by ACMA. You have the right to port your number when switching providers. Standard geographic numbers (02, 03, 07, 08) typically take 5-10 business days. Freecall 1800 and 13/1300 numbers can take longer. The porting process requires you to request the port from your new provider, who lodges it with the current provider on your behalf. You do not need to contact your old provider to start a port.

There is a risk of a brief interruption during the port cutover. A professional VOIP provider will manage the timing and advise you on how to minimise disruption. For more detail, see our guide on number porting in Australia.

1300 and 1800 numbers

If your business wants a national presence with a 1300 or 1800 number, VOIP makes this practical and affordable. 1300 numbers route calls to any Australian phone number you specify, charged at a local call rate to the caller. 1800 numbers are freecall to the caller, with the cost borne by the business. Both types are managed through your VOIP provider or a separate 1300 number provider. Costs start around $10-20 AUD per month plus per-call charges. See our guide on 1300 numbers for Australian business for full detail.

Your Next Steps

If you want to move from a basic ISP phone setup to a proper business VOIP service, here is the practical path forward.

• Check your internet connection quality. Use the VOIP Bandwidth Calculator to confirm your NBN connection can support the number of simultaneous calls you need.
• Work out how many users and lines you need. The Phone System Sizing Wizard helps you figure out the right setup for your team size and call patterns.
• Compare VOIP providers. See our guide to the best VOIP providers for Australian small business for a comparison of the main options.
• Confirm your number can be ported. Contact your prospective new provider with your existing number. They can confirm portability and give you a timeframe.
• Plan for power backup. If continuous availability matters, budget for a UPS for your modem and router. Around $80-150 AUD for a unit that covers a modem, router, and desk phone.
• Check any analogue devices. If you have a fax machine, alarm system, lift intercom, or EFTPOS terminal on a phone line, confirm compatibility with your VOIP provider before cutting over.

What internet speed do I need for VOIP?

VOIP calls use around 85-100 Kbps per simultaneous call. Speed is almost never the limiting factor. A standard NBN 25 connection supports dozens of simultaneous calls from a raw bandwidth perspective. What actually matters is consistency: low jitter (under 30ms), low packet loss (under 1%), and stable upload speed. A 25 Mbps FTTP connection with stable performance is better for VOIP than a 100 Mbps FTTN connection with variable jitter. Use the VOIP Bandwidth Calculator to assess your specific connection.

Can I keep my existing phone number when switching to VOIP?

Yes. Number porting lets you keep your existing number when moving to a new provider. The process is governed by ACMA rules in Australia. Standard geographic numbers (02, 03, 07, 08) take 5-10 business days. The new provider manages the port on your behalf. There is usually a brief interruption during the cutover moment. A good provider will manage the timing to minimise impact.

Does VOIP work in a power outage?

Not without battery backup. Your NBN modem and router need power to function. If the power goes out and you have no battery backup, your VOIP phones stop working. The solution is a UPS (Uninterruptible Power Supply), which costs around $80-200 AUD and provides 30-60 minutes of runtime. Many VOIP providers also support failover to a mobile number, so inbound calls are redirected to your mobile if your internet connection drops.

What hardware do I need for VOIP?

For a hosted VOIP setup, the minimum is an internet connection and either a desk phone (like a Yealink or Grandstream VOIP handset) or a softphone app on your mobile or laptop. If you want desk phones, you need VOIP-compatible handsets that connect via Ethernet, not analogue phones that plug into the green port. Your VOIP provider can supply or recommend compatible handsets and often pre-configure them for you.

How much does a business VOIP service cost in Australia?

Entry-level hosted VOIP plans start around $15-25 AUD per user per month, typically including unlimited local and national calls. Features like 1300 numbers, call recording, and CRM integration may be included or add-on costs depending on the provider and plan. Full detail including provider pricing is in our VOIP cost guide for Australian business.

Can I use my existing office phones with VOIP?

It depends on the type of phone. Old analogue cordless or desk phones (like a Panasonic or Uniden from JB Hi-Fi) connect via the green RJ11 port and are analogue. They can only work with VOIP through an ATA adapter. Modern VOIP desk phones (like Yealink, Grandstream, or Polycom) connect via Ethernet RJ45 and work directly with a VOIP service. If your current phones are connected to the green port on your modem, they are analogue phones, not VOIP phones.

Does VOIP work for 000 emergency calls?

Yes, business VOIP services support 000 emergency calling, but your service address needs to be correctly registered with your provider. Unlike traditional phone lines where your address was automatically on file with Telstra, VOIP providers ask you to supply a registered address for emergency services. Confirm this is set up correctly when you sign up with your provider. Do not assume it is automatic.

What is the difference between VOIP and a PBX?

VOIP is the technology that carries the call over the internet. A PBX (Private Branch Exchange) is the phone system that manages calls once they arrive at your business. A PBX handles hold music, call routing, ring groups, voicemail, and auto-attendants. With a hosted VOIP setup, the PBX is cloud-based and managed by your provider. With an on-premise setup, you run the PBX on your own hardware. VOIP is the transport. The PBX is the brain that directs traffic. You need both. See our guide on what a PBX is for more detail.