We have recently updated our Hosted PBX system to support busy lamp fields (BLF). This enables phones to monitor the status of other phones, so you can see if the phone in question is ringing, on or off hook. This is useful in a distributed office network, where you may not be able to see or talk to the other agent directly, to ascertain if they are on their phone or not.


As part of the BLF system, you can also pick up calls from monitored extensions, by simply pressing the key associated with the extension which is ringing.


This feature is configurable via the Selfcare website. In order to configure this on your phone, you need to browse to "Cloud PBX" then go to "Handsets". Here you will see a list of your handsets. Select the handset you wish to adjust and the centre window will populate with your current configuration settings.


Currently the Grandstream GXP 2135, 2140, 2160 and 2170 support BLF. The options within the configuration settings vary based upon the phone being configured, as their individual features vary.


You will notice your "Lines" settings, which is where you configure your accounts. In most cases, you will only have 1 Line configured, which will be your Hosted PBX extension. Below this, there is another section, titled "Virtual Keys". This is where you configure your BLF/Speed dial keys. You can use the keys assigned to accounts (otherwise known as Line keys) as BLF keys if you wish. Each key will provide you 5 options, which are no, line, blf, dial and manually. If you want to configure the button as BLF, then select BLF. This will then provide an additional drop down menu to the right hand side, which contains a list of Hosted PBX extensions you can select to monitor. Select the extension you wish to monitor, and then click save at the bottom. The phone will configure the new settings after a reboot.


There are a few caveats to the system, which are as follows..


  • While you can technically monitor any registered hosted PBX extension, the BLF function will only work if the handset in question supports our implementation of BLF. As such, only Grandstream handsets are officially supported. Other devices, if they support the PUBLISH method of BLF may work, but this is not supported. Please see the manual setup section at the bottom for more information on setting up BLF on devices which have not been supplied by ourselves.


If you find that you need to monitor many extensions (more than 4), we can supply Grandstreams extension kit (GXP2200), which is supported on the GXP2140 and GXP2170, which plugs into your existing handset and allows you to monitor 40 additional handsets. This is also fully configurable within selfcare. If you require further information or pricing information, please contact sales.


Call Pickup

You can use configured BLF keys to pick up calls from that extension, if it is ringing. In order to do this, firstly, you must enable "Allowed To Pick Up" on the extension settings page. Once you have done done this, and the BLF keys are configured on your phone, you can then pick up calls from the monitored extension simply by pressing the key when the phone being monitored is rung (the light will be flashing red on the phone). This will instantly answer the call on your phone, and the monitored handset will then stop ringing.


This feature is useful if a colleague is away from their desk temporarily, and allows you to answer their calls without having to adjust your number routing within selfcare.



Manual Setup

If you do not use our auto configuration platform, either because you use devices other than Grandstream devices, or because you want to maintain your phones yourself, then you will need to manually configure the BLF keys on your devices. 


Please note! Support on devices other than Grandstream devices is not currently proven. It may work, it may not.


Setup is very easy. 


  • You use your existing registration server address as your BLF server address (in most phones, you do not need to specify this, unless the BLF server is in a different location).
  • Enable Presence via PUBLISH in the phones account settings.
  • You then add the devices you are monitoring to the MPK (Multi-purpose Keys) on your device. You add these as the full SIP login name, so for example if you wanted to monitor extension 1001 on one MPK, you would add P-{PBX ID}-1001 as the data value.


That is all you need to do. As mentioned previously, this is not officially supported on devices other than Grandstream phones. However, as the PUBLISH method of BLF is fairly standard, the above should work on other devices. It is, however, not supported by ourselves.