For a long time, people got used to one simple idea: if the power went out, the landline often still worked.
That is no longer something a business should assume.
Modern phone systems usually depend on the same things as the rest of the office: power, network equipment and an internet connection. If one of those disappears, the desk phones can disappear with it.
The useful question is not just “will the phones work?” It is what happens to our business number if the office loses power or internet?
Why old landlines behaved differently
Traditional copper telephone services could often keep working during a local blackout because the line itself was powered from telephone infrastructure outside the building. A simple corded phone did not necessarily need mains power at your desk.
With NBN and VoIP services, the path is different. The phone may depend on an NBN connection box, router, network switch, phone system or other equipment inside the premises. Those devices need power.
NBN advises that equipment connected over the NBN network can be affected during a power blackout, and businesses should consider what other equipment their service relies on.
This is also why a cordless phone having a charged handset does not necessarily solve the problem. The base station, router or other equipment it connects through may still have no power.
What actually stops working when the power goes out?
For a typical small business, there can be several pieces between the phone on the desk and the outside world.
The NBN equipment may need power. The router or firewall needs power. A network switch supplying the phones needs power. The phone itself may also need power, either directly or through Power over Ethernet.
That means putting only one device on a battery backup can give a false sense of security. Keeping the NBN box alive does not help if the router beside it is off, and keeping the router alive does not help if the network switch feeding the phones is dead.
How can a business keep calls working through a short outage?
For a short power interruption, a correctly sized UPS can keep important communications equipment running. That may include the NBN equipment, router or firewall, network switch and the parts of the phone system that actually need to stay online.
It still needs to be tested. Battery age, the amount of equipment connected and the actual power load all affect how long a UPS will last.
Some older NBN FTTP installations also have an NBN battery backup unit, but that does not automatically power every other device needed for the phone service. NBN notes that separate equipment may still need its own backup power.
If the fixed internet connection itself fails, 4G/5G or another backup internet path may also keep the phone service online, provided the local equipment still has power and the backup connection is working.
What if the whole office is offline?
This is where a hosted phone system becomes particularly useful.
If the building is without power, the internet service is unavailable, or staff cannot get into the office, incoming calls do not necessarily have to keep trying to reach dead desk phones.
A hosted system can be configured so calls are redirected to nominated mobile numbers, another office or another answering point. Staff may also be able to use a mobile or software phone where the service and configuration support it.
The important part is that customers can continue calling the same published business number. They should not need to know which employee’s mobile to call because the office has lost power.
Q10 Voice can be configured around this kind of continuity planning, including routing calls away from an affected site where appropriate.
Mobile failover is useful, but it should not be treated as magic. Mobile networks can also be affected by widespread outages, congestion or local infrastructure problems. The goal is to have another path available, not simply move every dependency onto one mobile service.
For emergency calls, businesses should also avoid assuming an NBN-delivered phone service will always be available during a blackout. NBN recommends having another way to communicate, such as a charged mobile phone with coverage.
What should you test before the next outage?
You do not need to make this complicated. Turn the problem into a few practical questions.
If the office loses power, how long does the network stay online?
If the NBN connection goes down, do the phones have another internet path?
If the whole site is offline, where do incoming calls go?
Can staff answer the normal business number from somewhere else?
Has anyone actually tested the failover rather than assuming it works?
That last one matters. A backup plan that has never been tested is still mostly an assumption.
This is also one piece of the wider cyclone IT planning businesses in Townsville and Cairns should work through before severe weather arrives.
If you want to know what would actually happen to your phone system if the power, NBN or office disappeared tomorrow, Q10 can review the current setup and work through the practical failover options.