BLF Configuration for Polycom IP Phones using Asterisk IP PBX

Configuring Polycom IP Phones to use BLF (Busy Lamp Field) on Asterisk IP PBX

I have done a lot of Asterisk IP PBX installation using Polycom IP Phones and I consider them to be one of the leading providers of IP Phones.  They are highly configurable, easy to provision and deploy and are durable.

Lately, one of my client has asked me to implement a BLF or Busy Lamp Field.  BLF could be used in any Small to Medium sized businesses and Medical Offices and basically gives anyone a visual indicator of another extension’s phone state.  This is ideal and very useful for receptionists, secretaries, or anyone that answers phones for another person.

Asterisk 1.6 and higher supports BLF to a limited degree.  The feature is limited in that it cannot Publish the phone state so if someone has DND (Do Not Disturb) on or if a call is on HOLD, it will not register visually.  What it will do is visually show you when an extension is ringing, on a call or offline.  While lacking full BLF functions, this is plenty enough for a receptionist to know that a specific extension is not available and inform the caller.

Since Asterisk IP PBX is open source, there are tidbits of information here and there that you need to put together.  After searching long and hard, I will outline the configuration changes that need to be made for BLF to work.  I have to give it up to since a lot of the information was obtained from this site.  For Asterisk users, this site is full of useful information.

NOTE:  The older IP501 and 601 phones, which are legacy phones did not work with BLF.  Instead, you should use Buddy Watch for these older legacy phones.  I will cover Buddy Watch in a future article.  The following information was tested on IP450 and IP650 phones.


Asterisk IP PBX settings to enable BLF for Polycom IP Phones:

Edit extensions.conf:

  • Add the following lines in the context your phones use
    exten => _*8.,1,SET(GLOBAL(PICKUPMARK)=${EXTEN:2})
    exten => _*8.,n,Pickup(${EXTEN:2}@PICKUPMARK)
Edit sip.conf:
  • Add the following lines in the [general] section
    notifyringing = yes
    notifycid = yes
Edit MACAddress-phone.cfg:  Example:  0004f2458f6b-phone.cfg
  • Add the following lines in the MACaddress-phone.cfg  XML file  (Insert as many as you want inside the opening/closing tags)
    attendant.resourceList.1.address=”Extension #”
    attendant.resourceList.1.label=”Extension Label”
    attendant.resourceList.2.address=”2nd Extension”
    attendant.resourceList.2.label=”Extension Label”
    attendant.resourceList.3.address=”3rd Extension”
    attendant.resourceList.3.label=”Extension Label”
Once you have edited these config files, commit the changes to Asterisk, reload the config files, and reboot the IP Phones.  Once the phones come back online, you will see all of the Extensions you added.  Please note that these coded extensions have higher priority than the contacts you add to the phone.  Therefore, these will appear right after your Line Appearances and before your personal contacts.
When I implemented this feature, the receptionist was very happy as it gave her a quick representation of call status.  A good example is if someone calls for a doctor and they are currently on a call.  The receptionist can get this information quickly and notify the caller and process the call accordingly.  He/she could transfer the call directly to the doctor’s voicemail, park the call, or have them call back.  It’s all about the OPTIONS!


About Express Interconnect: We are a Portland, Oregon based Small Business VoIP Phone Consultant specializing in implementing quality VoIP PBX system based on Asterisk IP PBX. We can be reached at 503-820-3513 or via email at: and can help with any questions you might have.

Due to Demand, we have finally branched out into Hosted VoIP Phone Service for Small Businesses.  Our Hosted VoIP Service provides full Asterisk IP PBX functionality in a simple Plug and Play system.

Also, please make sure to visit our on-line store at VoIP Phones Direct for all of your IP Phone needs. We carry Grandstream, Polycom, Snom, Aastra, and Yealink IP Phones with a 14 day money back guarantee and FREE UPS Ground Shipping.

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  1. Small Business VoIP: Enable Asterisk BLF (Busy Lamp Field) in Yealink and Grandstream IP Phones « Asterisk How To « Small Business | Medical Office VoIP - April 23, 2012

    […] have outlined the BLF setting for Polycom IP Phones in my previous article which involved the MAC-address-phone.cfg file. However, with non-Polycom IP […]

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