BLF Example Scenario - Wiki

Check out our YouTube channel to watch our simple tutorials that will help you set up most of our features.

BLF Example Scenario

From Wiki

Jump to: navigation, search


Article en Français Artículo en Español
Français Español

Note: This feature is on a per request. Please contact our technical support via live chat or via ticket to have this enabled on the desired server.


This is a brief attempt to capture information which was necessary to achieve success in configuring "BLF" (Busy-Lamp-Field) feature on VoipPhones (Grandstream GXP2160 in this case) new deployment at a small office. For purposes of this summary / so it makes 'sense' I am providing 'context info' which is strictly speaking not necessary; but hopefully it will help provide clarity around the use-case scenario for this feature / and how to make it work (possibly).


New deployment of Voip phones in a small office. For purposes of discussion here, they have 4 Handsets, each with its own DID; and sub account configured for each VOIP Grandstream phone device. Inbound calls for the office are aimed at the 'reception' phone number; which points to a ring group; for which all 4 phones are members. Thus anyone in outside world calling in to the 'office number' will generate a ring on all 4 phones concurrently / and anyone in the group can pick up.

In some cases, one person picks up, talks briefly, and then wants to transfer the call to one of the other lines. It is useful to know prior to starting this process, if the person in question is already on their line / are busy and not available to take the call. The BLF feature allows you to see the "On-hook / Off hook / ringing" status of other lines in your office which you are monitoring.

The BLF "Busy Lamp Field" is (apparently?) a common feature on "old world" phone systems (aka this client had old Nortel phones that were being replaced; and they had BLF configured). Apparently people who talk on the phone lots - find it helpful. My client asked me to get it working, and it was indeed possible, and actually not too terrible at all once the proper steps were clear.

Concise Steps to Get it working

  1. Confirm if your phone handset device appears to support BLF feature. (note in my case I was working with GrandStream GXP 2160 handsets, and they do support this feature; as do apparently many other related grandstream 'business class' handset voip phones). I have the impression that many similar handsets from other vendors implement this feature. I have not tested any other handset for this feature.
  2. Decide what specific single VoipMS server these client devices must all be connected to. In the case of this example I will make that choice to be, ""
  3. Make a request to Voip.MS technical support via a ticket, where you specifically tell them, "I want to enable BLF feature for my account and all linked subaccounts, which are registered to the specific Voip.MS voip server,". They will enable features server-side which will allow these sub-accounts to monitor BLF status of other sub-accounts who are registered on the same / correct / designated voipMS server.
  4. Wait patiently for them to confirm back that they have done this. Until it is done, you must wait.
  5. Once it is done, login to the web-admin UI for each of the 4 handsets. Adjust the BLF setting as shown below, on each phone.
  6. Now, on each phone LCD display console you will have 3 BLF status indicators which list the NAME designated for each BLF monitoring; and the HOOK_STATUS will be apparent via colour coding. You are done. Test it, happy days.

More Detailed Steps to get it working

  • Background - BLF is effectively granting 'trusted devices' the permission to 'snoop' and 'notify' on call hook status with other trusted devices / that are all registered on the same specific VoipMS server. So you only configure a single SIP account on each hadnset. You do not provide credentials for multiple accounts on each handset. Rather, each handset authenticates (as per normal) to the SIP server with just one SIP account / and in addition to its normal call functions, you configure BLF so that you specifically designate "hey, this programmable button number one, corresponds to JOE_VOIP_PHONE_ACCOUNT with SIP_ACCOUNT_ID, and I want you to monitor and display his on-off-hook/call status to me please. And then programmable button nubmer two, corresponds to JANE_VOIP_PHONE_ACCOUNT with SIP_ACCOUND_ID_FOR_JANE, and I want same monitor display for her phone, adjescent to programmable button number two on my phone. Etc etc."
  • From what I can tell the grandstream phones I was working with support inherently 6 x programmable buttons out of the box with no-questions-asked for BLF monitoring if desired. It seems that it might? be possible to add more lines / buttons; but I am not sure; haven't tested; and don't have easy physical access ot the phones still so I am not inclined to test beyond the use case I already have any know. If you want BLF for more than 6 neighbour devices, you will need to play with it yourself and then update the wiki to tell the world what you have learned :-)
  • So, here is a concrete example to nail it all home.
  • For the client's office in question, We have SIP sub-accounts defined, as follows
  1. 123456_user1 / 1SecretPass / 101 / JOE SMITH is user of this phone
  2. 123456_user2 / 2SecretPass / 102 / JANE SMITH is user of this phone
  3. 123456_user3 / 3SecretPass / 103 / JIM JONES is user of this phone
  4. 123456_user4 / 4SecretPass / 104 / JOHN JAMES is user of this phone.
  • Login to webadmin UI for Joe's phone, as an admin user (default user-pass is admin / admin)
  • proceed to the ACCOUNTS menu, GENERAL settings, and then punch in required settings to make this phone active and registered. That will include setting
  1. (ENABLED = YES)
  2. (ACCOUNT NAME = Human legible name for easy identification, is not passed to server)
  3. (SIP SERVER = )
  4. (SIP USER ID = 123456_user1 and also AUTHENTICATE ID = 123456_user1 )
  6. SAVE AND APPLY and then go back to GENERAL > ACCOUNT STATUS page, this account should be listed now next to ACCOUNT 1 / with a green block to indicate it is active. Make a test call if you feel like it.

This is what it will look like at this stage: Blf-example-1.png

  • To configure BLF monitoring:
  2. In the first row starting with "1" click the "EDIT VPK" Button at right-hand edge.
  3. In the pop-up dialog, designate the following information
    4. VALUE = 123456_user2
  4. once you have entered values as designated above, click SAVE. Then repeat this process for all the remaining BLF buttons you wish to configure / people hook status you wish to monitor.
  5. note here we are working on JOE phone, so we do NOT configure BLF for JOE phone; rather we will configure 3 x BLFs for (JANE, JIM, JOHN). Similarly, on JANE phone we would configure 3 BLFs, for JOE / JIM / JOHN. etc etc).
  6. Note when you pop open the second entry "EDIT VPK" the Grandstream may try to be helpful and propose to you, that you wish to use "account 2" not "account 1". Don't fall for this, it is a trick! (ie, not what you want to do).
  7. Click SAVE VPK
  8. once you have configured the 3 x BLFs you will see something like this:


  • you are now done, that is it.
  • There should now be 3 x names listed next to buttons on the LCD Console of phone, labelled respectively, JANE JIM JOHN.
  • call Jane's phone from your cell phone, and watch the "LED" blink. When the phone is answered, note the change of status. Happy days.

Footnote - related topic - Transfer calls

  • It was mentioned as an aside but not specifically stated. If you wish to be able to transfer calls from one SIP_SUBACCOUNT to ANOTHER_SIP_SUBACCOUNT, then the process is straightforward but does require you do a few specific steps, ie
  1. First, in each of your SUB_ACCOUNTS you must explicitly designate an "INTERNAL EXTENSION" (this is done near the bottom of the 'sub account' config page) and note presently VoipMS force us to have "10" as the first 2 digits of any extension. Note that all extensions must be unique within your VoipMS account / as all your Sub-account IDs must also be unique. So, get those config pieces in place and document them.
  2. Once the sub-accounts are registered (on the same server) and have extensions assigned, you can use transfers as per the phone manual for "BLIND TRANSFER" with no more effort. A possible example use-case might read like this
    1. JOE answers his phone (ext.101)
    2. JOE talks to person briefly, then tells them, "HANG ON I will transfer you over to JANE"
    3. WHILE CALLER IS STILL ON THE LINE, press TRNF button on your voip telephone; and key in the number of the handset you’re transferring to (JANE is EXT.102) and then press SEND button, and HANG UP.
    4. It should ring on JANE's handset, she can answer the phone normally and speak with the caller you were talking to a moment ago.
  1. If you want to take it to the next level, and enjoy that kind of thing. These grandstream phones have a 1-click feature you can configure in the WEB_UI of the phone, SETTINGS > CALL FEATURES; scroll down the page and locate "AUTO ATTEND TRANSFER" and set it to YES instead of the "NO" which is default.
  2. Now that you have saved this feature on one phone, do it on all the phones in the office.
  3. and now, you can do attended transfers, ie, before you throw the caller over to Jane you can talk to Jane first and tell her, "Hey, that guy from yesterday, yeah he is calling back, here he comes ok?". The feature works exactly as described on handy-dandy 'concise feature card' one of which I attach here for the grandstream phone in question just for simplicity.


Note: full original PDF was taken from external public source, URL [1]

Personal tools
Actions Blog
Guides (Français)
Guías (Español)