Problem : the Fxo is busy when we have incoming call

Unanswered Question
Jan 21st, 2008
User Badges:


i have IPCC that is co-resident with CCM 4.3, the problem is when i receive one call from outside and i want terminate without speaking with agent, the FXO port remains busy and i must configure shut and no shut do activate it.

Please help me.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4 (1 ratings)
pcameron Mon, 01/21/2008 - 06:19
User Badges:
  • Cisco Employee,

This is likely due to Supervisory Disconnect ... the phone company expects the users on either side of the network to drop calls on loop start trunks.

When the PSTN caller hangs up after the IPCC has answered the call, as far as the phone company is concerned, the call was answered and they are waiting for the called party to clear the call down. Since the IPCC is playing a message (your call is important,please wait/the queue is only nine hours long/relax and listen to some easy listening hits ...) , the FXO port is off hook and it will stay off hook until the destination party on the IPCC terminates the call, or someone pulls out the cable and drops the connection.

This is not a router/voice card problem - everything is working as designed !!! The telephone network expects calls to be hung up by the users on both sides - the telephone network does not hang up loop start trunks towards subscribers.

Here is a note on CCO that gives some more background -

So the best way to fix it ?

From the IP phone on you network, ring someone on the PSTN, then have them hang up on you. Do not hang up your phone. After a short time, you <> hear some kind of repeating tone pattern indicating the far end has disconnected. This is called a disconnect tone and the voice port DSP's can listen for this and automatically drop the call after a short timeout.

These disconnect tones vary from country to country. We need to know where you are , so we can make a suggestion about the best way to configure the voice port to detect the tone and drop the call.

Can you tell us where the router is located, and also post the SH RUN.

If you do a search on netpro for 'disconnect supervision' or 'disconnect tone' you will get quite a bit more background on this issue - it happens all the time ...

dbenattou Mon, 01/21/2008 - 09:39
User Badges:


thank you for reply. I'm in Morroco (North Africa), now i cannot post the sh run because i'm out of the office, but if it's possible you can post me the config of disconnect tones that i can apply to my 2811 Router.

Thanks at advance.

paolo bevilacqua Mon, 01/21/2008 - 11:12
User Badges:
  • Super Gold, 25000 points or more
  • Hall of Fame,

    Founding Member

Usually it will be a busy tone. Have the caller hang-up and listen, if you cannot recognize the tone, you can either record from a PC with microphone, or do a wireshark capture, reassemle the audio file and post it here.


This Discussion