[asterisk-users] Correct settings for UK (BT) FXO

Faris Raouf asterisk at raouf.net
Thu Sep 14 15:05:09 MST 2006

Brian Candler wrote:
> Is there a document somewhere giving the correct TDM400P FXO settings for
> use on a BT PSTN line in the UK? All I can find is
> http://www.voip-info.org/wiki/view/UK+Asterisk+Details

A patch was written for a previous version of Asterisk that got halfway 
there. I found some bugs in it which took us all the way and it worked 
perfectly. The original patch and my modifications and some other 
modifications/enhancements were added in a later release version of 
Asterisk but unfortunately for no apparent reason although it worked in 
other EU countries it no longer does so in the UK. I'm afraid I forget 
the exact details.

Unfortunately I've not had time to investigate the code to try and 
figure out what is going on and how to fix it.

Basically it is all down to the polarity switches that happen or don't 
happen on hangup. What is really required is for the code to sense the 
constant tone you get when you hangup in the UK, but this is far too 
complex for me to be able to deal with.

So personally I've given up on analog and I'm sticking to the digital 
realm of ISDN. One day I may invest in a Sipura FXO box (or are they now 
Linksys or something?) which does sense the disconnect tone.

Incidentally I think there are people on this list who have no issues 
with the TDM400p in the UK, but I have no idea how/why.


More information about the asterisk-users mailing list