Setting Busy Lamp Field (BLF) on Linksys SPA942

This post doesn’t document a success.

Try as I might, and despite other people obviously having success with Trixbox and Asterix, I have not been able to get a working BLF on the Linksys 942 with the provider VOIPfone.

They publish notes on their support for busy lamp on the Snom series of phones, but they state that their custom SIP system doesn’t necessarily work with other vendors. Snom themselves document their BLF support.

I don’t blame VOIPfone for what is otherwise a great VOIP service but I would like to get it working!

So what have I done?

The following line entered against an extension under the admin advanced GUI on the SPA942 should work:



sd means speed dial (so one can call 204 with a single button push, this works!). It is the extension entry in the ‘sub=’ portion of the command that indicates the extension number to be dialled.

204@$PROXY is the extension number of the extension you want to monitor, and $PROXY is a shorthand that substitutes the name of the SIP server (in my case I use the VOIPfone PBX service so your format of extension number may well differ.

vid=1 may well not be needed but it forces the entry to use the defaults from line 1 which is of course defined to be a registered extension with VOIPfone. This is supposed to be the default action anyway.

The diagram below shows the entry in situ:

All that happens is that the light associated with line 2 blinks amber, meaning there is an issue.

This posting does throw some light on it being a Linksys specific thing but using the ‘usr=’ format of command didn’t appear to make any difference to me.


3 thoughts on “Setting Busy Lamp Field (BLF) on Linksys SPA942

  1. Paul Rausch November 24, 2009 at 8:54 pm Reply

    Saw your pingback, re: my post on BLF. I’ve never been able to get BLF working over NAT. I’m not sure exactly why but it just doesn’t seem to work, that may be your issue. Anyway, best of luck, if you figure it please leave a comment on my article so that I can share the fix with everyone!

  2. Robert Baird July 16, 2013 at 3:20 am Reply
  3. BigR July 16, 2013 at 7:28 am Reply

    I will dig out the SPA and give it a try, thanks!

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