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
Section titled “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:
Step 1: Define the BLF function key
Section titled “Step 1: Define the BLF function key”-
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.
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Select the Function Keys tab.
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Add a function key that watches the extension you want to monitor. The example below sets up monitoring for extension 1004.

- 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.
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Click Save.
Step 2: Push the change to the phone
Section titled “Step 2: Push the change to the phone”- Go to Auto Provisioning > Phones and click the refresh icon
next to the phone you configured. Cloud Voice asks whether you want to reprovision it. - Click OK in the confirmation dialog.
What you’ll see
Section titled “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.
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.