BLF Example Scenario - Wiki

BLF Example Scenario

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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

  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.
  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

  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:


Footnote - related topic - Transfer calls

  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. Open ticket with VoipMS friendly support team, and ask, "Please enable call transfers between all my account-and-subaccounts / for those accounts who are registered on the same SIP server, in my case here"
  3. wait patiently until they confirm back
  4. Once they tell you it is good, 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]

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