Presence and Busy Lamp Field (BLF)

How does BLF / Presence work?

Presence and Busy Lamp Field (BLF) is a light on an IP phone showing presence information of any other extensions connected to your account.

BLF works through the SIP protocol by making use of SUBSCRIBE and NOTIFY messages sent to your phone advising the current state of any other phones on your account that have also subscribed to your BLF list. Once the status of any monitored extension changes from idle to busy or vice versa, the other subscribers are notified by our CloudPBX with the change in status by acknowledging the NOTIFY SIP message with a 200 OK SIP message.

Quick Guide

Enabling the BLF is a two step process requiring a small configuration against your phone and secondly enabling BLF against YourCloudPBX line.

Setting up Presence and BLF on CloudPBX

  1. Log into YourCloudPBX > select the number you want to use Presence & BLF.
  2. Select CloudPBX > Advanced >Presence and BLF.
  3. Click Enable Presence/BLF on this line only.
  4. Click Save settings to update.

Setting up BLF on your Polycom

  1. Settings > Directories > Contacts Directory > 1.
  2. Add (+) : Name, Last Name (optional), Contact (requires full number including country / area code)
  3. Protocol –> SIP (only for VVX500, 600)
  4. Watch Buddy –> Enable
  5. SAVE
  6. Select contact –> Add to favorites (if you want the contact to appear on the home screen of your keypad).
  1. Select DSSKey tab
  2. Select the line key you wish to monitor
  3. Set Type to BLF
  4. Set Value to the phone number you wish to monitor – NB requires country / area code (e.g. 61289707500)
  5. Directed Group Pickup: On Extension column set each BLF number to *89 (see picture below). NB – *89 enables a caller within the BLF group to pick up another BLF phone using the BLF key (see also Short Keys).
  6. Click Confirm to save and apply

When configured, the LEDs should light up accordingly on your Yealink.

  • Green: extension is available. Press BLF key to dial extension.
  • Red: extension is on a call
  • Blinking red: extension is receiving a phone call. Press BLF key to perform pick-up.

Setting up BLF on your Cisco SPA

  1. Logon to the phones Web UI (Settings | Network | Current IP)
  2. Type [IP address]/admin/advanced (see screenshot below)
  3. Phone Tab | Line Key 1
  4. Paste and edit the following function into Extended Function: fnc=blf+sd+cp;sub=61390444888@call.sipcity.com.au;usr=61390444888;nme=Betty
  5. SAVE | reboot the phone

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