Monitor Extension Status by BLF Key on Fanvil IP Phone
A Busy Lamp Field (BLF) key lets one phone keep an eye on another extension. Once assigned, the key’s LED reflects that extension’s live call and Do Not Disturb (DND) state, and a single press dials the line or answers its ringing calls. This walkthrough uses a Fanvil X6U-V2 running firmware 2.12.1 as the reference model; the portal steps are the same for other auto-provisioned Fanvil handsets.
Before you begin
Section titled “Before you begin”The Fanvil phone must already be provisioned through Cloud Voice Auto Provisioning (the PBX pushes each phone’s settings to it automatically, rather than you typing them into the handset) and have an extension assigned to it. If that isn’t set up yet, work through Auto Provision Fanvil IP Phone with Cloud Voice first.
Step 1: Define a BLF function key on the extension
Section titled “Step 1: Define a BLF function key on the extension”-
Sign in to the PBX web portal and open Extension and Trunk > Extension, then edit the extension that belongs to the Fanvil phone.
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Open the Function Keys tab.
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Set up a key to track another extension. The example below monitors extension 1004.

- Type: Choose BLF.
- Value: Pick the extension you want to monitor from the drop-down list.
- Label: Optional text shown next to the key on the phone screen.
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Click Save.
Step 2: Push the change to the phone
Section titled “Step 2: Push the change to the phone”Saving in Step 1 stores the BLF key in the extension’s configuration on the PBX. The key only shows up on the physical handset after you reprovision the phone.
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Go to Auto Provisioning > Phones and click the refresh icon
next to the phone you just edited.
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When prompted to reprovision the phone, click OK.
Result
Section titled “Result”The BLF key’s LED now tracks the monitored extension (extension 1004 in this example) in real time:
- Solid green: The extension is idle.
- Solid red: The extension is placing or is on a call.
- Solid yellow: The extension is in DND.
- Flashing red: The extension is ringing.
- LED off: The extension is unregistered or has been removed from the system.
Pressing the BLF key lets you:
- Call the monitored extension directly.
- Answer an incoming call ringing on the monitored extension.