---
title: Twinnings
section: features
summary: "Twinning rings a user's external device (mobile or Teams) in parallel with their PBX extension, so incoming calls reach them wherever they are."
updated: '2026-08-12'
---

> **Twinning** also rings an external number (mobile phone or Microsoft Teams) when a user's PBX extension is called, so they can be reached on another device.

## Overview

Twinning is configured per user. A rule has an active status so you can pause it without deleting it.

## What it does

The dial strategy sets how the external device is reached. Fixed-Mobile Convergence (FMC) extends PBX features like transfer and hold to the mobile device, and applies to mobile twinning that uses a GSM-capable strategy.



## See also

- [Users](users.md) - the parent entity for twinning configurations.
- [Queues](queues.md) - enable "ring twinnings" on a queue to reach twinned members on mobile.

```yaml fields
status_boolean:
  label: Enabled
  tab: General
  hint: 'Whether twinning is on. When off, incoming calls only ring the PBX extension.'
phone_number:
  label: 'Phone number'
  tab: General
  hint: 'The external number to ring alongside the PBX extension.'
type:
  label: Type
  tab: General
  hint: 'The destination type for twinning.'
  values:
    -
      value: mobile
      label: Mobile
      text: 'Rings a cellular phone number.'
    -
      value: teams
      label: Teams
      text: 'Rings a Microsoft Teams client.'
dial_strategy:
  label: 'Dial strategy'
  tab: General
  hint: 'How the outbound leg to the external device is placed.'
  when: 'Type is Mobile'
  values:
    -
      value: gsm_only
      label: 'GSM only'
      text: 'Traditional cellular call. Most reliable but uses mobile minutes.'
    -
      value: voip_only
      label: 'VoIP only'
      text: 'IP-based call to the mobile app. No mobile minutes but needs a data connection.'
    -
      value: voip_and_gsm_fallback
      label: 'VoIP and GSM fallback'
      text: 'Tries VoIP first. Falls back to GSM if the app does not answer in time.'
delay:
  label: 'Ring after'
  tab: General
  hint: 'Seconds to wait before ringing the external device. Set to 0 for true simultaneous ring.'
fmc_enabled:
  label: FMC
  tab: General
  hint: 'Enables Fixed-Mobile Convergence (FMC), allowing call transfer and hold to be performed directly from the mobile phone. Available only on a Voxbi SIM.'
backup_phone_number:
  label: 'Backup phone number'
  tab: General
  hint: 'Secondary number tried when FMC is on and the primary number is unreachable.'
  when: 'FMC is on'
```