# Control a Fanvil IP Phone from the Cloud Voice App Desktop

CTI (computer telephony integration) mode links a Fanvil desk phone to the desktop Cloud Voice App when both use the same extension. The audio still runs through the physical phone, but the app becomes an on-screen control surface for placing, answering, and managing those calls.

This applies to the Fanvil models that support CTI with the desktop Cloud Voice App. See the [list of compatible Fanvil phones](/pbx/desktop-client-user-guide/cloud-voice-app-desktop-client-cti-overview/#linkus-web-client-cti__compatible-fanvil).

:::tip
Using a phone that isn't on the compatible list? Follow [Control an Incompatible IP Phone from the Cloud Voice App Desktop](/pbx/desktop-client-user-guide/remotely-control-an-incompatible-ip-phone-by-cloud-voice-app-desktop-client/) instead.
:::

## Before you begin

Two conditions must be met before CTI mode will work:

- **PBX server**: The uaCSTA (user agent CSTA) connection must be turned on at **PBX Settings > SIP Settings > Advanced > Other Options > Enable uaCSTA Connection**. uaCSTA is the control channel that lets the app operate the desk phone over SIP (Session Initiation Protocol, the signaling used for VoIP calls). Your administrator controls this setting.
- **Desk phone**: The Fanvil phone must be registered with the same extension you use in the desktop Cloud Voice App.

:::caution
Register only one account on the Fanvil phone. If more than one account is registered, CTI may stop working.
:::

## Step 1. Make the desk phone controllable

:::note
If your administrator provisioned your extension to the phone through Auto Provisioning, the phone is already prepared for CTI. Skip ahead to [Step 2](#step-2-switch-the-app-into-cti-mode).
:::

When the extension was registered manually, enable uaCSTA on the phone yourself. The steps below use a Fanvil X5S as an example; other models follow a similar flow.

1. Sign in to the phone's web interface and open **Line > SIP**.
2. In the **Line** drop-down, choose your extension.
3. Open the **Advanced Settings** section and type your extension number into the **uaCSTA Number** field.
4. Open the **SIP Global Settings** section and select **Enable uaCSTA**.
5. Click **Apply**.

## Step 2. Switch the app into CTI mode

Putting the desktop Cloud Voice App into CTI mode lets you drive calls on the paired Fanvil phone from your computer.

1. Sign in to the desktop Cloud Voice App.
2. In the top-right corner, click the CTI icon ![CTI mode toggle](/images/pbx/cti.png), then pick your connected Fanvil phone from the list.

   ![Selecting the paired Fanvil phone in the app's CTI menu](/images/pbx/fanvil-cti-mode-desktop.png)

## What you can do

Once CTI mode is active, you can handle the following from the app while the Fanvil phone carries the audio:

- Place and end a call
- Start a second call
- Answer or reject an incoming call
- Record a call
- Transfer a call, either attended or blind
- Hold and resume a call
- Swap between held calls
- Flip a call