"NORMAL_CIRCUIT_CONGESTION" has nothing to do with the busy tone. There should be problem with your TDM card(sangoma).
You can firstly check if your link and cic state are normal before you dial the call. To check the state, you can either check the freeswitch.log or use "wanpipe" trace.
 
 windy
 2013-11-19
From： Nandy Dagondon
Send： 2013-11-19  07:59:23
To： FreeSWITCH Users Help
CC：
Subject： Re: [Freeswitch-users] Ignore busy signal when dialling out on anFXO port
Please post your dialplan snippet.

Re POTS line requiring you to dial 9. Usually this is a PABX access code to grab the LINE e.g. to get a dial tone but 9 is not dialed. Only the numbers following 9 is actually dialed to the POTS line.  Unless ... this is an unusual setup. 

/nandy

On Mon, Nov 18, 2013 at 3:41 PM, Oren Hecht <orenhe@in.taldor.co.il> wrote:
Hi,
 
I'm new to freeswitch so please excuse me if I'm not using the right terms.
 
I have freeswitch connected to a POTS line using an FXO port, and I am trying to use it to dial out without success.
The POTS line requires me to dial '9' first to get a line for dialing out, and as long as I don't press 9 it gives a 'busy' tone.
I am trying to bridge an extension to freetdm port with adding a '9' prefix, but I get "Failed to open channel" and the reason is "NORMAL_CIRCUIT_CONGESTION". When I look at 'ftdm dump' I see: "last_state: BUSY".
 
I guess the reason for failure is that freeswitch hears the busy tone and thinks the line is not free and aborts. I also thought this is related to the early media signaling so I tried adding {ignore_early_media=true} thinking it will ignore the busy tone, but it dodn't help.
 
How can I tell freeswitch to ignore the busy signal and just dial the destaination number, (the '9' prefix will give it a free line)?
 
Thank you very much for the help,
Oren Hecht.

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