BLF (Busy Lamp Field) — Busy Lamp Field
What is BLF (Busy Lamp Field)?
BLF (Busy Lamp Field) is a desk phone or softphone feature that shows the real-time status — idle, ringing, or on a call — of another user's extension as a small light or icon next to a speed-dial button. It's commonly used by a receptionist or team lead who needs to see at a glance which colleagues are free before transferring a call to them, without having to call and ask first.
More detail
BLF status is typically shown as a colored light (green for available, red for busy, flashing for ringing) mapped to a programmable key on a desk phone or a contact row in a softphone.
BLF relies on the same underlying presence and call-state signaling the phone system already tracks, surfaced as a simple visual indicator rather than a separate status system.
Frequently asked
- Who typically relies on BLF the most?
- Receptionists and front-desk staff who transfer calls frequently rely on BLF heavily, since it lets them see which colleague is free before attempting a transfer, avoiding sending a caller to someone already on another line.
- Is BLF the same as presence?
- They're closely related — BLF is typically a physical or on-screen indicator light showing another extension's call state, driven by the same underlying presence and call-state data a UCaaS platform tracks more broadly.
See also
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