📲

Fixed Mobile Convergence

Fixed Mobile Convergence: One Number, Any Device

📲 Fixed Mobile Convergence (FMC) is a Cloud PBX feature that ties a single business phone number to multiple devices at once: your desk phone, mobile, and computer. A call to that number rings all of them simultaneously. You answer on whichever is nearest.
This page explains how FMC works, why it matters for businesses in Luxembourg and the Greater Region, and what to look for when evaluating it.

How Fixed Mobile Convergence Works

When a caller dials your business number, the Cloud PBX system routes that call to every device registered under your profile. Your desk phone rings in the office. Your mobile rings in your pocket. Your laptop softphone rings in a browser tab. The first device you pick up answers the call; the others stop ringing.
If you are already on a call on your mobile and return to the office, you can transfer the live call to your desk phone without hanging up. The caller hears no interruption. This is sometimes called a "hand-off" or "seamless transfer."
Behind the scenes, the Cloud PBX handles the routing entirely. No hardware changes are needed on the caller's side. From the caller's perspective, they dialled one number and reached you. They never need to know which device you used.

Why It Matters for Your Business

  • One number to share: Staff publish a single direct number on business cards, email signatures, and directories. No need to list a separate mobile number.
  • Reachability wherever you are: Missed calls drop when staff are away from their desks. FMC eliminates that gap by extending the office number to the mobile.
  • Professional appearance on outbound calls: When staff call clients from their mobile, the caller sees the business number, not a personal mobile number.

What to Look For

  • Simultaneous ring vs. sequential ring: Simultaneous ring routes to all devices at once. Sequential ring tries each device in a queue. Simultaneous is faster; sequential gives more control. Confirm which mode your provider uses.
  • Mobile app quality: FMC depends on a mobile app. Test call quality, battery behaviour, and reliability on both Wi-Fi and mobile data before signing a contract.
  • Cross-border coverage: For businesses operating across Luxembourg, Belgium, Germany, and France, confirm the provider supports FMC across all four countries without extra fees.
📋 How the "One Number" Works in Practice
Your Cloud PBX assigns one Direct Inward Dialling (DID) number to your profile. DID is a standard that lets a carrier route calls to a specific extension inside a phone system. When that number receives a call, the system checks which devices are registered to your profile and sends the call to all of them at once. You can add or remove devices from your profile through a web portal, usually without needing IT support.
📱 Using FMC on a Mobile Device
FMC on mobile works through a VoIP app installed on your smartphone. VoIP (Voice over Internet Protocol) means the call travels over your data connection rather than the standard mobile network. This keeps the call tied to your business number regardless of which SIM card or country you are in. Most providers offer iOS and Android apps. Some also support a browser-based softphone for computers.
🔄 Transferring a Call Between Devices
Mid-call device transfers, sometimes called "call hand-off," let you move an active call from one device to another without the caller noticing. A common scenario: you answer a call on your mobile while leaving the office, then transfer it to your desk phone once you arrive at a meeting room. The feature is available in most enterprise Cloud PBX platforms. Check whether your provider supports it on all device types, including mobile-to-desktop and desktop-to-mobile.
🌍 FMC for Cross-Border Teams
Many businesses in Luxembourg work across borders daily. An employee may spend Monday in Luxembourg City, Tuesday in Trier, and Wednesday in Metz. Without FMC, they need to give clients multiple numbers or forward calls manually. With FMC, they keep one number that follows them across countries. The only requirement is a data connection: Wi-Fi or mobile data. Calls made from abroad still show the Luxembourg business number on the recipient's screen.
💰 Cost Considerations
FMC is included as a standard feature in most Cloud PBX subscriptions. There is usually no extra charge for registering multiple devices under one number. However, calls routed over mobile data may consume data allowance, and some providers charge extra for mobile app licences. Ask your provider whether the mobile app is included in the base licence or billed per user. Also confirm whether outbound calls from the app are billed at the same rate as desk phone calls.

Frequently Asked Questions

Does FMC work when I am abroad?
Yes, if you have a data connection. FMC relies on a VoIP app, which uses internet data rather than a local SIM. When travelling in the EU, your roaming data allowance typically covers this. Confirm with your provider whether there are any country-specific restrictions.
Will my personal mobile number be visible to callers?
No. When you make or receive calls through the FMC app, the caller sees your business number. Your personal number stays private. This is one of the main reasons businesses adopt FMC for staff who work from personal mobile phones.
What happens if I do not answer on any device?
If the call is not answered on any registered device, it follows your normal call handling rules: voicemail, a colleague's extension, or an auto-attendant message. These rules are configured in your Cloud PBX dashboard and apply to all devices under your number.
Can I use FMC on a tablet or computer as well as a phone?
Yes. Most Cloud PBX providers offer apps for iOS, Android, Windows, and macOS, as well as browser-based softphones. You can register as many devices as the provider allows under your profile. All registered devices ring simultaneously when your number receives a call.
Is Fixed Mobile Convergence the same as call forwarding?
No. Call forwarding redirects a call from one number to another, usually sequentially. FMC rings multiple devices registered to the same number at the same time. The distinction matters for response time and for outbound caller ID: with call forwarding, outbound calls from a forwarded device show the forwarding number. With FMC, outbound calls always show the original business number.
📅 Ready to explore Cloud PBX for your business?
Start with the provider comparisons or feature guides. If you want expert help, book a short call with a consultant.
Book a Demo | Compare providers | Explore features

Related Features

  • Mobile Application — Make and receive business calls from your smartphone using your office number
  • Softphone — Use your computer as a desk phone without any additional hardware