Replacing an office phone system: what to check first.

An old office phone system is a box on the wall with copper lines running into it. Its replacement is software. The system runs on a server or in the cloud, calls travel over the internet connection, and a handset, a computer and a mobile app can all be the same extension. The change is worth making, and it goes well when a few things are settled before anything is ordered.

1. The network comes first

A voice call needs very little bandwidth, but it needs it steadily. Delays and dropped packets that nobody notices while a web page loads turn into choppy audio and calls that cut out. Before the phones move, check three things:

• The internet connection has enough upload capacity for the busiest hour, with room left for everything else the office does.
• The router can give voice traffic priority over downloads and video. This setting is usually called quality of service.
• The switches and cabling are sound, and can power the handsets over the network cable if that is the plan.

The firewall also needs to be set up for the phone system. Audio that only travels one way, and calls that drop after a fixed time, usually come down to this. 3CX publishes the ports and settings its system needs, linked below.

2. Decide how calls should flow

This is the part people remember. Walk through a call from the outside: who answers during business hours, what happens if they do not, what callers hear after hours and on public holidays, and where voicemail goes. Then do the same for each team that takes calls. A one-page diagram agreed in advance saves weeks of adjusting things after launch.

3. Keep your numbers

Existing numbers can almost always move to the new provider. This is called porting. The account details must match the current provider’s records exactly, the move is booked for a specific day, and the old service has to stay active until it completes. Cancel the old lines first and the numbers can be lost.

The provider that carries the calls is connected to the phone system by a SIP trunk. It replaces the copper lines, and is usually priced by the number of calls that can run at once, not by the number of extensions.

4. Handsets, headsets or apps

Not everyone needs a desk phone. Reception, and anyone who transfers calls all day, usually prefer one. People who are mostly at a computer are often happier with a headset and the desktop app, and people on the road use the mobile app so the office number follows them. Mixing all three is normal.

5. Plan for the day it is down

A phone system that runs over the internet stops when the internet does, and equipment connected to the nbn does not work in a power blackout. Decide in advance what should happen: calls diverting to mobiles, a backup mobile data connection for the office, or a battery supply for the network cupboard. If anyone relies on the office phones to call Triple Zero, tell staff what to use if those phones are down.

Cutover day

1. Build and test the new system alongside the old one, using temporary numbers.
2. Train the people who answer the most calls before the switch, not after it.
3. Port the numbers on a quiet day, with someone watching the first calls come in.
4. Keep the old system connected until every number is confirmed as working.
5. Review the call flow after two weeks, when real use has shown what needs changing.

We set up, host and manage 3CX, and look after the network it depends on. See 3CX and Network Services.