Standard Business Voice
Everyday calling
Consider
Normal inbound + outbound
For offices with normal inbound and outbound calling requirements.
Capacity inputs
Reception activity
Employee count
Peak concurrent calls
Business hours
C9 GROUP · SIP TRUNKING
Keep your phone system. Modernise the connection behind it.
If your existing phone system still works for the business, you may not need to replace it just to modernise your calling.
C9 designs and manages SIP trunking around your existing phone system, business numbers, call volumes, connectivity and future voice plans.
Existing PBX compatibility reviewed
Eligible numbers can be migrated
Call capacity sized to your business
Migration managed by C9
Trusted by Australian businessesIn good company. Trusted by businesses across Australia.
CHECK SIP FIT
Start with the phone system you already have.
C9 reviews the PBX, numbers, call capacity, connectivity, network readiness and future voice plans before recommending a SIP path.
START WITH YOUR SITUATION
Start with the phone system you already have.
SIP Trunking should solve the actual voice requirement: retain a working PBX, replace an underlying service, increase capacity or prepare for a future cloud transition.
Current PBX
Your current PBX still does the job?
Keep the compatible phone system and modernise the voice connectivity behind it.
Service replacement
Your existing voice service needs replacing?
Review the current phone numbers, PBX, network and calling requirements before changing services.
Call capacity
Need more simultaneous calls?
Size SIP capacity around peak call volumes instead of simply counting phones or extensions.
C9 VOICE CONTEXT
SIP trunking is one component of the business calling environment.
The SIP service matters. But so do the PBX, business internet connection, firewall, phone numbers, call routing and future voice direction.
SIP is one part of the calling path
The service matters, but so do the PBX, business internet connection, firewall, numbers and call routing.
Numbers and routing need mapping first
C9 identifies important numbers, where calls need to go, and what should happen when requirements change.
Future voice direction stays visible
If Teams Phone or cloud calling is coming later, C9 can assess whether SIP should support that transition.
CHOOSE YOUR VOICE PATH
Modernise what needs changing. Keep what still works.
C9 compares existing PBX + SIP, multi-site SIP and future cloud or Teams pathways before recommending the next step.
Existing PBX + SIP
For businesses with a compatible phone system that still meets their operational needs. Keep the PBX and replace the underlying voice connectivity.
Multi-Site SIP
For businesses that need voice services across multiple offices, stores, clinics or operating sites.
Cloud / Teams Transition
For organisations planning to retire the existing PBX and move towards Microsoft Teams Phone or another cloud voice platform.
SIP CAPACITY PATHS
Buy the call capacity the business actually needs.
The number of employees is not the same thing as the number of simultaneous calls. C9 looks at peak calling behaviour before recommending capacity.
See FAQBrowse plans
Size Standard Voice
Customer-Facing Voice
Higher inbound
Consider
Queues + peak periods
For organisations with higher inbound activity across sales, service or operational teams.
Capacity inputs
Call queues
Main numbers
Department routing
Peak periods
Overflow requirements
Multi-Site & High-Volume Voice
Complex capacity
Consider
Sites + continuity
For more complex environments where multiple sites or higher concurrent calling volumes need to be accommodated.
Capacity inputs
Number ranges
Multiple locations
Centralised call routing
Higher concurrent call volumes
Business continuity requirements
C9 confirms available SIP services, channel requirements, call inclusions, number requirements and commercial terms after reviewing your existing environment.
SIP TRUNKING ESSENTIALS
The trunk is only useful if the environment around it is ready.
C9 reviews the PBX, number inventory, concurrent call needs, connectivity, firewall configuration and continuity requirements before the service moves.
PBX compatibility
The existing phone system should be reviewed before a SIP service is ordered.
Number inventory
Know which main numbers, direct numbers and number ranges are active before migration planning begins.
Concurrent calls
Capacity should be based on expected simultaneous calling rather than extension count alone.
Connectivity
Voice relies on the IP path carrying it. Available bandwidth, latency and network behaviour need to be considered.
Firewall and voice configuration
SIP configuration needs to work correctly with the network and existing telephony environment.
Call continuity
Important inbound calls should have an agreed routing approach for relevant outage scenarios.
VOICE PERFORMANCE
Call quality is not controlled by the SIP trunk alone.
A business voice problem can originate in several places, which is why C9 assesses the calling path rather than treating SIP as an isolated product.
Connectivity
The IP connection carrying the call
Bandwidth, latency and stability affect the voice path.
Network
Routers, switches and QoS
Local configuration can change the experience even when the SIP service is healthy.
PBX
The existing phone system
Compatibility and configuration need to match the proposed voice service.
SIP
External calling connectivity
The trunk connects the phone environment to external calling.
Endpoints
Phones and user devices
Phones, headsets and user behaviour still influence call experience.
C9 recommendation
If the business relies on voice for sales, service, bookings or operations, C9 reviews the full path: SIP service, PBX, network, connectivity, routing and continuity.
LEGACY VOICE VS C9 MANAGED SIP
Modern voice connectivity without replacing working technology unnecessarily.
Use this as the decision matrix before replacing a phone system that may still be useful.
Existing PBX
C9 Managed SIP
Compatible PBX can be retained.
Traditional / standalone voice setup
Existing architecture remains unchanged.
Call capacity
C9 Managed SIP
Sized around concurrent calling requirements.
Traditional / standalone voice setup
Often tied to historical service configuration.
Number migration
C9 Managed SIP
C9 manages the agreed migration process.
Traditional / standalone voice setup
Customer coordinates.
Network readiness
C9 Managed SIP
Connectivity and local network are considered.
Traditional / standalone voice setup
Often treated separately.
Call routing
C9 Managed SIP
Routing requirements reviewed during design.
Traditional / standalone voice setup
Existing configuration only.
Future migration
C9 Managed SIP
Teams/cloud direction can be considered now.
Traditional / standalone voice setup
Separate future project.
Support
C9 Managed SIP
C9 provides one managed-service relationship across applicable components.
Traditional / standalone voice setup
Voice and network may sit with separate parties.
MANAGED SIP
The value is not simply connecting a trunk.
The value is getting the complete calling environment from its current state into a supportable one, with PBX, network, numbers and routing handled together.
Assess: PBX, network, numbers and call requirements.
Design: SIP service, capacity, routing and continuity.
Migrate: Coordinate service and eligible number transition.
Validate: Test important inbound and outbound call behaviour.
Manage: Keep one C9 contact path for the voice services under management.
WHY PARTNER WITH C9
Voice, network and IT considered together.
Keep existing investment where it still makes sense
Replacing the whole phone system is not automatically the right answer.
Migration starts before porting
Numbers, dependencies and call flows are reviewed before the cutover is scheduled.
Network issues do not get ignored
C9 can assess the network environment supporting the phone service rather than looking at the carrier connection in isolation.
A path beyond the existing PBX
When the business is ready for Microsoft Teams Phone or another cloud calling environment, the wider voice roadmap can be reviewed.
One accountable relationship
C9 remains involved across the services it manages instead of handing the business a SIP username and walking away.
C9 SIP DELIVERY
From existing voice environment to managed SIP.
Review PBX, business numbers, existing voice service, connectivity and call requirements.
Confirm architecture, concurrent capacity, routing and migration requirements.
Configure the agreed environment and coordinate number-porting requirements.
Move the agreed services and validate important inbound and outbound calling.
Keep C9 involved for support, changes, capacity reviews and future voice requirements.
ACTIVE STAGE
Audit
Review PBX, business numbers, existing voice service, connectivity and call requirements.
SIP Trunking FAQs
SIP trunking provides IP-based connectivity between a compatible business phone system and external telephone networks.