Modernise your telephone connectivity without necessarily replacing your phone system.
Solutions · Business Communications · Business Telephony · SIP Trunks
A SIP trunk is an internet-based telephone service that connects a compatible business phone system, supported Microsoft Teams setup or certain simpler telephone devices to the public telephone network.
Change the connection without changing everything
A suitable older phone system may sometimes be retained by using a media gateway that converts between the phone system's existing ISDN connection and the SIP trunk. Compatibility must be checked before this approach is recommended.
Useful for staged modernisation
A SIP trunk can separate the decision about telephone connectivity from the decision about replacing the whole phone system, reducing unnecessary change where existing equipment remains suitable.
When a SIP trunk may fit
- Provide external connectivity for a supported Microsoft Teams design
- Connect supported simpler telephone equipment where a full hosted system is unnecessary
- Link one or more sites while retaining an appropriate existing system
Retain a compatible existing business phone system
Replace analogue (PSTN) or digital (ISDN) connectivity
Move to internet-based calling in stages
A SIP trunk is not a complete phone system
A SIP trunk provides telephone connectivity. It does not automatically provide all of the call-handling, call-distribution or call-routing functions of a complete business phone system.
The existing phone system, Teams setup or connected device remains responsible for many user features. Compatibility, capacity and support boundaries therefore need to be checked across the complete design.
Connectivity and resilience
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Compatible phone system or device
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Suitable internet connection
- Local network and firewall configuration
- Power
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Required call capacity
- Phone-system failure behaviour
- Incoming and outgoing call failover
- Telephone-service provider dependency
Number transfers, emergency calling and mobility
Telephone numbers and number porting should be planned before migration. Existing telephone services should not be cancelled until the port has completed successfully. Emergency-calling arrangements must also be planned.
A SIP trunk does not by itself determine how mobile or flexible the workforce can be. That depends mainly on the phone system, Teams setup or devices connected to it, including whether they support mobile working or hot desking.
Legacy line-connected services, including lift alarm lines or elevator remote monitoring systems, alarm signalling, telecare, warden call systems, personal triggers and monitoring services, should be checked with the relevant supplier. Older fax equipment also requires specific compatibility assessment.
Compare the complete service
Compatibility, supported equipment, required call capacity, number-transfer process, emergency-calling arrangements, failover options, support boundaries and current commercial terms must be verified for the specific customer design before commitment.
Emergency calling
Business telephony services may depend on mains power, internet connectivity, network equipment and correctly configured telephone services.
Calls to 999 and 112 should be available from appropriately configured services, but emergency-calling behaviour can vary depending on the telephone system, provider, device and location.
If phones, applications or users move between sites or are used remotely, the location information associated with an emergency call may not reflect the caller’s actual location. Callers should therefore clearly state their location and provide a reliable callback number.
Customers should keep site and service-location information up to date and consider how emergency calls will be made during a power, internet or equipment failure.
In an emergency, call 999 or 112. Do not contact FVC Solutions instead of the emergency services.
Modernise only what needs to change
We can assess whether a SIP trunk is the right route for your existing system, Microsoft Teams environment or simpler telephone requirement.