SIP Trunking

Think of a SIP Trunk as a digital phone line that connects your office phone system (usually a modern PBX) to the outside world, using your existing internet connection instead of traditional copper wires.

Whereas old phone lines use physical cables for each call, like having a separate, dedicated "pipe" for every conversation, a SIP Trunk uses your high-speed internet to carry all your voice calls. It's like having one big, versatile digital highway over the internet that can handle many calls at the same time.

A channel in the context of SIP trunks is essentially a single, concurrent call path that allows one call (inbound or outbound) to be active at any given time.

Think of a SIP channel like a traditional telephone line: if you have 10 lines, you can have 10 people talking simultaneously. Similarly, if you have 10 SIP channels, you can support 10 concurrent calls.

Determining the required number of SIP channels you require is a bit trickier and depends on your business's call volume and usage patterns. The professional and accurate method uses the Busy Hour Call Attempts (BHCA) Metric to calculate a factor known as Erlang B. A simpler rule of thumb for many small to mid-sized offices is as follows:

• Typical Office (General employees, light phone use) - 1 channel for every 4-5 phones
• Moderate/Sales Team (Regular, consistent phone use) - 1 channel for every 3 phones
• Call Center/High-Volume (Agents on the phone all day) - 1 channel for every 2 phones

Note that its always worthwhile to give a 20-30% buffer for peak times.

When you don't have enough channels, users will frequently experience busy signals or failed calls when trying to make or receive external phone calls.

Here are the key signs that you need more channels:

Too Many Busy Signals: When someone tries to call out from your telephone system, they get a fast, repeating busy tone right away, or the call fails with an error message, even though the person they're calling isn't busy. This happens because all your lines are currently tied up with other people's conversations, so there's no channel left for this new call.

Incoming Callers Can't Get Through: People calling into your organisation frequently complain that they get a busy signal or the call simply drops/fails before it even starts ringing anyone. This is because your system can't bring the incoming call in because there are no channels free to accept it.

Problems Happen at the Same Time: These problems only seem to happen during peak business times. This is when the maximum number of people are trying to use the phones, pushing you over your limit.

There is no need to panic however as this is an easy problem to fix. Additional channels can be quickly added to the trunk alleviating the issue.

Absolutely! We can port your existing phone numbers to our SIP Trunk service from any provider. The process can take up to 6 weeks if its a complex number port but you can use the new SIP Trunk, showing the correct Caller ID number during this period.

No. We will set up the SIP Trunk service for no charge however there is a charge to port your existing number(s). See the Pricing page for more information.

We can set up your SIP Trunk within 1-2 business days however a number port can take up to 6 weeks. Note that we can show your correct Caller ID for outgoing calls in the meantime.

Choosing between a Pay As You Go (PAYG) and an Unlimited plan often comes down to how much you use your phone lines.

Pay As You Go (PAYG)

This is like a pre-paid mobile phone or a utility bill where you only pay for exactly what you use. You pay a small channel fee for the SIP trunk itself, and then you are billed for every call as per the provider's rate plan.

Its best for businesses with very low call volumes or with highly seasonal or unpredictable calling patterns.

The Upside: You keep your monthly fixed cost low.

The Downside: If your call volume suddenly spikes, your final bill could be unexpectedly high.

Unlimited Plans

This is like a fixed monthly subscription that includes all or a majority of your calls. Its like a flat fee for an internet or streaming service that is not usage based. Note however that a Fair Use Policy applies for this service so it is not abused.

You pay a higher, channel fee for the SIP trunk and in return, you get unlimited calling to local, national and mobile numbers. Note that it does not include some numbers such as 13/1300, International, special services etc.

Its best for businesses with high or consistent call volumes or that need predictable budgeting without worrying about fluctuating call costs.

The Upside: You get complete budget certainty—no surprise bills, no matter how much you talk.

The Downside: If you have a slow month and don't make many calls, you still pay the same fixed price.

We offer configuration assistance to your PBX technician to set up the new SIP Trunk on your PBX and if you are experiencing any issues with the service.

Note that we cannot support your PBX system in any way and the expectation is that your PBX technician would contact us after initial analysis of a problem with the service.