In short: A multi-site phone system connects several offices, branches or schools to one phone system, with a single extension range, local numbers for each site, central or distributed answering, site-specific out-of-hours rules and emergency locations, automatic diverts if a site goes offline, and central administration and reporting. Cloud platforms make this far simpler than linking separate PBXs.
What a multi-site phone system does
When each office has its own phone system, transferring a call to a colleague in another building means a second outside call, and every site has its own supplier, contract and quirks. A multi-site phone system puts every location on one platform:
- One dial plan and extension range, so anyone can reach anyone with a short extension number and transfer calls between sites as internal calls
- Local numbers for each site, so customers can keep dialling the branch number they know
- Central or distributed answering: one reception for everyone, or each site answering its own calls with overflow to the others
- Site-specific rules for opening hours, holidays and out-of-hours messages
- Central administration, so users, menus and groups for every site are managed in one portal
- Organisation-wide reporting, so you can see call volumes and missed calls by site
Because a cloud phone system already runs in a data centre, adding a site is mostly a matter of connectivity and devices. See what is a cloud phone system? for the basics.
Designing call flows across sites
The technology is the easy part; the call flow is where multi-site organisations win or lose. Decide early:
- Who answers first? A central team for all sites, each site for itself, or a mix (for example branches answer locally and overflow to head office).
- What happens when nobody answers? Overflow to another site, a queue, a mobile or voicemail, and after how long.
- Which rules are local? Opening hours, bank holidays, closures and emergency messages often differ by site.
- Which numbers are shown? Whether outbound calls present the local branch number or a central number.
- Who can change what? Local managers may need to switch on a closure message without access to the whole system.
For teams that handle a lot of calls centrally, a call centre phone system adds queues, wallboards and reporting on top.
Emergency calls and site locations
With one phone system spread across many buildings, the location given to the emergency services on a 999 or 112 call has to be right for each site, and ideally each floor or building on a large campus.
Each platform handles this differently. In Microsoft Teams Phone, emergency addresses are created in the Teams admin centre and assigned to users or numbers, and can be tied to network locations, with places for a floor or building. In Webex Calling, each location in Control Hub has its own address, numbers and PSTN connection. On hosted platforms such as Forever UC and 3CX, the address is registered against each number with the provider. Whichever you choose, keep the records up to date as people and sites change, and remember that users on mobile apps and at home need their location handled too.
Resilience when a site goes offline
One of the biggest benefits of a cloud system for multi-site organisations is that the phone system itself is not in any one building. If a site loses its connection or power:
- Calls can divert automatically to another site, a central team or mobiles
- Staff with softphone apps can keep working from mobiles or home
- The rest of the organisation is unaffected
The weak point is each site's connectivity. Larger sites often justify a leased line and a backup connection, with a network that prioritises voice; see hosted VoIP for what that involves. If you keep an on-site PBX at some locations, SIP trunks can be configured to fail over to another site or to mobiles.
How each platform handles multiple sites
| Platform | How multi-site works |
|---|---|
| Hosted 3CX | One system for every site. Multi-site support is part of the PRO edition and above, and licensing is sized by simultaneous calls across the whole system. See 3CX editions |
| Microsoft Teams Phone | One tenant for the whole organisation, with auto attendants and call queues per site, emergency addresses per location, and PSTN options that can be mixed in one tenant |
| Forever UC | A hosted service, so every site and home worker connects to the same platform, with menus and department groups set centrally; Forever UC Contact adds live contact centre reports |
| Webex Calling | Organised by locations in Control Hub, each with its own numbers, time zone and PSTN connection |
| SIP trunks | Connect one or more on-site PBXs to the network, with failover between sites |
For a side-by-side view across every factor, see cloud phone systems compared.
Branches, surgeries and multi-academy trusts
Multi-site needs show up in many sectors: retail and trade branches that want local numbers with central reporting; healthcare practices running several surgeries from one appointments team; professional firms with regional offices; and multi-academy trusts sharing one system across schools while keeping each school's own number, menus and term-time schedule. For schools, see school phone systems.
Whatever your structure, the move usually happens site by site, with number porting planned for each location. Contact us with a list of your sites and we will design the call flow and recommend a platform.
Why choose your cloud phone system with Forever Systems
We are vendor-neutral. Forever Group supplies and supports several cloud phone platforms, so we recommend the one that fits how your organisation works rather than the one we happen to sell.
- Side-by-side comparison of hosted 3CX, Microsoft Teams Phone, Forever UC, Forever Teams and Webex Calling for your users
- Contact centre and call recording options matched to your call volumes and CRM
- Number porting, handsets and set-up handled for you, including the move off analogue and ISDN lines
- Connectivity checked so call quality is right from day one
- UK support for moves, adds, changes and faults
- For BT Cloud Voice, see our BT Business Partner site cloudvoice.cloud
We work with businesses, schools, charities and public sector organisations. We do not sell consumer phone services.
Want a vendor-neutral cloud phone system comparison and quote?
Tell Forever Systems what you need and we will come back to you by email with options, not a hard sell.
Contact usFrequently asked questions
Can I have different numbers for each office on one phone system?
Yes. A multi-site cloud phone system can hold local numbers for every site, each with its own menu, opening hours and answering rules, while staff share one extension range and can transfer calls between sites internally.
Can calls transfer between sites without going over the phone network?
On a single multi-site phone system, calls between extensions at different sites are internal calls, so they do not go out over the public phone network. Call charges depend on your platform and plan, so check how internal calls are treated.
What happens if one site loses its internet connection?
The phone system runs in the cloud, so other sites carry on. Calls to the affected site can divert automatically to another site, a central team or mobiles, and staff with mobile apps can keep working over mobile data.
Does 3CX support multiple sites?
Yes. 3CX lists multi-site support as part of its PRO edition, and the AI edition above it. One 3CX system can serve several offices, with licensing sized by simultaneous calls across the whole system rather than per site.
How do emergency calls work on a multi-site phone system?
Each site, and ideally each building or floor, needs a correct emergency address registered with the platform so 999 calls give the right location. Teams Phone, Webex Calling and hosted platforms each have their own way of doing this.