# Monitor Extension Status by BLF Key

A Busy Lamp Field (BLF) key lets one desk phone show, at a glance, whether another extension is free, busy, or ringing. This page walks through assigning a BLF key from the Cloud Voice web portal so the key tracks a specific extension's call activity and Do Not Disturb (DND) presence.

Because the phone is auto-provisioned, you configure the key centrally in the portal and push it to the device, no manual setup on the handset itself.

## Before you start

The target phone must already be connected to Cloud Voice through Auto Provisioning and have an extension assigned to it. If you still need to set that up, see:

- [Auto Provision IP Phones Remotely via RPS Method](/pbx/administrator-guide/auto-provision-ip-phones-remotely-rps-method/)
- [Auto Provision IP Phones Remotely with Proxy](/pbx/administrator-guide/auto-provision-ip-phones-remotely-with-proxy/)

## Step 1: Define the BLF function key

1. Sign in to the Cloud Voice web portal and go to **Extension and Trunk > Extension**, then open the extension assigned to the phone for editing.
2. Select the **Function Keys** tab.
3. Add a function key that watches the extension you want to monitor. The example below sets up monitoring for extension 1004.

   
   ![Cloud Voice, a function key set to type BLF with extension 1004 chosen as the monitored value](/images/pbx/set-up-blf-key-monitor-extension.png)

   - **Type**: Choose **BLF**.
   - **Value**: Pick the extension to monitor from the drop-down list. In this example, choose `1004`.
   - **Label**: Optional. Whatever you enter here appears next to the key on the phone's screen.
4. Click **Save**.

## Step 2: Push the change to the phone

1. Go to **Auto Provisioning > Phones** and click the refresh icon ![refresh icon](/images/pbx/refresh.png) next to the phone you configured. Cloud Voice asks whether you want to reprovision it.
2. Click **OK** in the confirmation dialog.

:::caution
Reprovisioning pushes the saved configuration down to the phone. Many phone models reboot to apply the change, which briefly drops the phone's registration and any call in progress on that device. When possible, reprovision while the phone is idle.
:::

## What you'll see

Once the phone reprovisions, the BLF key's LED reflects the live status of the monitored extension (1004 in this example):

- **Solid green**: The extension is being monitored and is currently idle.
- **Solid red**: The extension is placing or on a call, or its presence is set to Do Not Disturb.
- **Flashing red**: The extension is ringing.
- **LED off**: The extension is unregistered or has been removed from the system.

:::note
Some Fanvil phone models can distinguish DND from an active call, showing DND as a **solid yellow** LED instead of red. Check with your Fanvil supplier for the models and firmware versions that support this.
:::

You can also press the BLF key to act on the monitored extension:

- Dial the monitored extension directly.
- Answer a call that is ringing on the monitored extension.

:::note
Call pickup only works when the Extension Pickup feature code is turned on. Enable it under **Call Features > Feature Code > Call Pickup > Extension Pickup**.
:::