Keep Your PBX. Upgrade Your Lines.
Summit SIP trunks replace your old PSTN lines with VoIP — cutting call costs, adding flexibility and delivering clearer calls over our own network.
Overview
If your business has invested in an on-premises PBX, you do not need to throw it away to move to VoIP. Summit’s SIP trunks connect your existing phone system to our voice network over the internet, replacing expensive PSTN and ISDN lines with flexible, scalable VoIP channels.
The result is lower call costs, the ability to add or remove channels as your business needs change, and access to features like geographic number flexibility and Microsoft Teams integration. And because Summit owns and operates its own network (ACMA Carrier Licence #388), your SIP trunks benefit from genuine Quality of Service prioritisation — not just a best-effort internet connection with fingers crossed.
For businesses that are not ready for a full cloud phone system but want the cost savings and flexibility of VoIP, SIP trunks are the ideal bridge. You keep the PBX you know and trust, and Summit handles the voice connectivity.
Key Benefits
Lower Call Costs
SIP trunks replace per-line PSTN charges with per-channel VoIP pricing. National calls cost a fraction of traditional line rates, and you only pay for the channels you need. Most businesses see a significant reduction in their monthly telephony spend from the first bill.
Protect Your Existing Investment
Your on-premises PBX still has years of life left. SIP trunks let you keep that investment while modernising the connection to the outside world. There is no need to retrain staff on a new system or reconfigure your entire call flow — your PBX continues to work exactly as it does today.
Scale Channels On Demand
With PSTN lines, adding capacity means ordering new physical lines and waiting for installation. With SIP trunks, adding a channel is a configuration change. Need extra capacity for a busy season? Add channels. Quiet period? Scale back down. You only pay for what you use.
Crystal-Clear Call Quality on Our Own Network
Data plans start from 10 GB, with options to scale up as your usage requires. Whether you need a lean plan for a single POS terminal or a more generous allocation for a temporary office with multiple users, we will match the plan to your actual needs.
Geographic Number Flexibility
The hardware is compact, easy to deploy, and portable. Move it between sites as your business needs change. Your static IP stays the same.
Microsoft Teams Integration
Like all Summit services, your 4G with static IP connection is backed by our Melbourne-based support team. You are not navigating a consumer support queue — you are talking to business specialists who understand your setup and your needs.
Built-In Redundancy
Data plans start from 10 GB, with options to scale up as your usage requires. Whether you need a lean plan for a single POS terminal or a more generous allocation for a temporary office with multiple users, we will match the plan to your actual needs.
One Bill, One Provider
The hardware is compact, easy to deploy, and portable. Move it between sites as your business needs change. Your static IP stays the same.
How It Works
Assess Your Current PBX
Summit reviews your existing phone system to confirm SIP trunk compatibility and determine the optimal configuration. We work with a wide range of PBX vendors and can advise on any firmware updates or settings changes needed.
Design Your SIP Trunk Configuration
We determine how many concurrent channels you need based on your call volumes, configure your number presentation (DIDs), and set up any failover rules.
Provision and Test
Summit provisions your SIP trunks on our network, provides the connection credentials for your PBX, and works with you to test inbound and outbound calls before going live.
Port Your Numbers
Your existing phone numbers are ported to Summit’s network so your customers, suppliers and marketing materials remain unchanged. Porting is coordinated to avoid any interruption.
Go Live with Ongoing Support
Once live, Summit monitors your SIP trunks and provides Melbourne-based support whenever you need it. Adjustments to channel counts, number presentation or routing can be made quickly.
Features
Voice Quality & Network
- QoS Prioritisation — Voice traffic prioritised on Summit’s own network for consistent call quality
- HD Voice — Wideband audio support for compatible handsets and PBX systems
- Jitter Buffer Management — Network-level jitter management to smooth call audio
- Redundant Voice Infrastructure — Summit’s voice platform is hosted across resilient infrastructure with multiple failover paths
Channels & Numbers
- Flexible Channel Counts — Start with as few as 2 channels and scale to hundreds as your business grows
- DID Numbers — Direct Inward Dialling numbers so callers can reach specific extensions directly
- Geographic Number Presentation — Present local numbers from any Australian area code
- Number Porting — Bring your existing numbers to Summit at no additional cost
- 1300 and 1800 Compatibility — Route inbound 1300 and 1800 numbers through your SIP trunks
Integration & Compatibility
- Broad PBX Compatibility — Works with a wide range of on-premises PBX systems from leading vendors
- Microsoft Teams Integration — Direct Routing for external calling through the Teams interface
- Fax over SIP (T.38) — Fax support for businesses that still require fax capability
- DTMF Support — Reliable touch-tone signalling for IVR menus and automated systems
Reliability & Failover
- Automatic Failover — Configure alternate routing destinations if the primary connection is unavailable
- 4G Backup Compatibility — Pair with Summit’s 4G Backup for automatic internet failover, keeping SIP trunks operational
- Dual Registration — Register SIP trunks at multiple sites for site-level redundancy
Management & Reporting
- Call Detail Records — Detailed records of all inbound and outbound calls for billing reconciliation and analysis
- Usage Reporting — Track channel utilisation to right-size your SIP trunk count
- Real-Time Monitoring — Visibility into trunk status, registration health and call quality metrics
Support for all of the leading phone systems
Summit SIP Trunks are compatible with all of the leading phone system vendors either via direct IP or interfaced with ISDN BRI, ISDN PRI or PSTN SIP Gateways.
Microsoft Teams SIP Trunks
Integrate your Microsoft Teams or Skype for Business with Summit SIP Trunks for a true Unified Communications Solution.
Tested with Sangoma, Sonus and AudioCodes for crystal clear Skype for Business Phone Calls.
Use Cases
The Business with a Working PBX
A 30-person engineering firm has a reliable on-premises PBX that handles their call routing perfectly. But their PSTN lines are expensive and inflexible. SIP trunks replace those lines with VoIP, cutting their monthly call costs while keeping their entire phone system unchanged. The team notices no difference except the lower bill.
The Multi-Site Organisation
A franchise group with offices in Melbourne, Sydney and Brisbane needs each location to present a local number while routing overflow calls between sites. SIP trunks with geographic DID numbers let each office present its local area code, and inter-site call routing is handled by the PBX over the SIP trunk — at no per-call cost.
The Microsoft Teams Workplace
A professional services firm has standardised on Microsoft Teams for internal communication but needs external calling capability. Rather than replacing their PBX, they use Summit SIP trunks with Teams Direct Routing. Staff make and receive business calls within the Teams app, while the PBX continues to handle advanced routing, queues and IVR in the background.
The Seasonal Business
An events company handles four times its normal call volume during peak season. With SIP trunks, they scale from 5 channels to 20 for the busy months, then back down again — paying only for what they need, when they need it. No new lines to order, no installation delays, no wasted spend in the quiet months.
Frequently Asked Questions
How many channels do I need?
A channel supports one concurrent call. As a rule of thumb, most businesses need approximately one channel for every three to four staff members. Summit will review your call patterns and recommend the right number of channels -- and you can adjust up or down at any time.
Can I keep my existing phone numbers?
Yes. We port your existing numbers to Summit's network at no additional cost. The porting process is coordinated to ensure there is no interruption to your incoming or outgoing calls.
What happens if my internet goes down?
SIP trunks can be configured with automatic failover to redirect calls to a mobile number, an alternate site, or a voicemail system. If you also have Summit's 4G Backup service, your internet connection itself fails over to 4G, keeping your SIP trunks operational without any manual intervention.
Do SIP trunks support fax?
Yes. Summit's SIP trunks support T.38 fax over IP for businesses that still require fax capability. For a fully digital alternative, consider Summit's Fax to Email service.
How do SIP trunks integrate with Microsoft Teams?
Summit offers Direct Routing for Microsoft Teams, allowing your team to make and receive external phone calls through the Teams interface. Your PBX handles the call routing while Teams provides the user experience. Our team will work with your IT provider to configure the integration.
What call rates apply?
Summit offers both pay-as-you-go and bundled call rate options for SIP trunks. National fixed-line and mobile call rates are competitive with or better than traditional PSTN pricing. We will provide a detailed rate schedule during the quoting process.
Is there a minimum contract term?
Summit offers flexible contract terms for SIP trunks. We will discuss the options that best suit your business during the quoting process.
Why Choose Summit for SIP Trunks
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We Own the Network Your Calls Travel On
Most SIP providers are reselling someone else’s voice platform over someone else’s internet. Summit owns and operates the network (ACMA Carrier Licence #388), which means we control the quality from end to end. When you pair Summit SIP trunks with a Summit internet connection, your voice traffic gets genuine network-level QoS — not a marketing promise.
Eliminate the Blame Game
When call quality drops, is it the SIP provider or the internet provider? When Summit delivers both, there is no question and no finger-pointing. One team owns the entire voice path and can diagnose and resolve issues without waiting for a third party.
Melbourne-Based Voice Expertise
Summit’s support team is based in Melbourne and understands PBX systems, SIP configuration, and voice networking. When you call with a SIP trunk issue, you speak to someone who can read a SIP trace and configure your trunk — not someone reading from a script.
Broad PBX Compatibility
Summit has been connecting Australian businesses since 2000. We understand that a 4G connection at a construction site or a remote POS terminal is just as important to your business as the fibre link at your head office.
Ready to Move Your PBX to VoIP?
Get a SIP trunk quote tailored to your PBX, your call volumes and your business. We will make the transition seamless.