BLF (Busy Lamp Field) and Function Keys

Overview

The Busy Lamp Field (BLF) feature of your Virtual-Call Cloud PBX shows the status of other extensions or selected functions directly on the phone or in the Virtual-Call UC Client. Through programmable function keys, you can quickly see whether a colleague is currently on a call and trigger functions like listening to voicemail, switching presence status, or executing a speed dial with a single key press.

Function keys are configured per extension and are available both on compatible desk phones and in the UC Client. Frequently used key assignments can be saved as a template and applied to other extensions.

Prerequisites

• Administrator access to the Virtual-Call Cloud PBX
• At least one configured extension
• Desk phone with programmable function keys (for display on the phone) or Virtual-Call UC Client

Configuring Function Keys

Function keys are configured per extension in the Function Keys tab.

1. Navigate to Extension and Trunk → Extension.
2. Click Edit next to the desired extension.
3. Open the Function Keys tab.
4. Configure the following fields for each key.
5. Click Add to create additional keys.
6. Click Save.

Key Fields

Typical Key Assignments

Function Key Templates

If multiple extensions should receive the same key assignment, you can create a template and apply it to other extensions. This saves time when setting up new extensions or updating the assignment for an entire department.

Creating a Template

1. In the Function Keys tab, click Apply Function Keys Template.
2. In the dialog, click Add.
3. Enter a Name for the template (e.g., Sales Template).
4. Optional: Enter a Remark.
5. Configure the keys as for a normal extension (Type, Value, Label).
6. Click Save.

Applying a Template

1. In the Function Keys tab, click Apply Function Keys Template.
2. In the dialog, select the desired template from the list.
3. Click Apply.
4. The template's keys are transferred to the extension.

Function Keys in the UC Client

Configured function keys are also displayed in the Virtual-Call UC Client (Desktop, Mobile, Web). Users see the BLF status of their colleagues and can trigger functions with a click without requiring a desk phone.

Typical Scenarios

Scenario 1: BLF for a team

• Configure one function key per team member that points to the colleague (value = extension number).
• The keys show at any time who is currently on a call, free, or in DND status.
• With a key press, calls can be transferred or forwarded to the colleague.

Scenario 2: Quick access to voicemail and status

• Assign a key to *2 for “Listen to Voicemail”.
• Assign additional keys to presence codes (e.g., *91 Available, *92 Away).
• Users can change their status with a single key press.

Scenario 3: Uniform assignment for a department

• Create a template “Sales” with BLFs on all sales colleagues plus voicemail and status keys.
• Apply the template to all new sales extensions.
• Update the template centrally when the team composition changes and reapply it.

Best Practices

• Use short, clear labels—space on the keys is limited.
• Group keys by function: BLFs on colleagues together, feature codes together, speed dials together.
• Use templates for uniform assignments within a department—this saves time and ensures consistency.
• Document templates with meaningful names and remarks.
• Check the number of available keys on your desk phone before planning assignments—some devices support only a few programmable keys.
• Test BLF displays after configuration: Call a monitored extension and check whether the display changes correctly.