Busy Lamp Field (BLF): Watching Lines, Queues and Voicemail
A BLF key is a button on a desk phone with a light that shows what another line is doing. Green means free, red means on a call, and flashing red means ringing, so you can press it to pick the call up. BLF keys can also watch call queues and voicemail boxes.
Last reviewed: October 2026
| Light | Meaning |
| Green | Free. Press to call. |
| Solid red | On a call, or on do not disturb |
| Flashing red | Ringing. Press to answer it. |
Watching a colleague's line
- In the portal, open the line you want to watch and choose Other Settings → Line Monitoring. Tick Enable Monitoring for the Line and save.
- In Voice → Phones, edit the phone that will do the watching. Set a spare key to BLF and choose the line. See Programming phone keys.
- Save and restart the phone.
If you set up phones by hand, set the key type to BLF and the value to the full number or the extension's Login, not the short extension number.
Watching a voicemail box
A mailbox key flashes red when there are new messages. Press it to listen.
With a phone set up through the portal, choose Mailbox Monitoring as the key type and pick the mailbox. The portal turns on monitoring for that mailbox for you.
By hand, open the number's Voicemail settings and tick Enable mailbox monitoring through SUBSCRIBE events. Then set a BLF key with VM after the number, for example 61370500989VM.
Watching a call queue
Open the queue's settings and tick Support BLF monitoring and call pickup directly from the queue. The queue must use the Ring All strategy. A BLF key for the queue flashes when callers are waiting, and pressing it answers the longest-waiting caller.
Do not disturb
Lines on do not disturb show solid red. See Do not disturb and call screening.
Not lighting up?
Wait a minute, or restart the phone to make it ask for the status again.
Still need help?
Our Australian support team is available to assist you.