FXO not disconnecting

Answered Question
Oct 16th, 2009

I have a 2800 Series router with 12.4-15.T1 with 4 FXO ports in it. These ports are connected to another system that forwards calls onto another phone - long story, but it saves huge long distance $$ over satellite phones.

The issue is the system gets calls from auto-dialers (solicitors) that call the system and don't seem to hangup when the remote phone is busy/not available/off line.

What this does is leave the FXO port open and the call leg up. Because of this the router sends a CDR to our billing system saying this call has been up for hours/days or worse!

Is there anyway to have the FXO turn off after so many seconds if there are no voice packets?

Any ideas would be appreciated.



Correct Answer by Paolo Bevilacqua about 7 years 4 months ago

Also configure frequency 425 under dualtone disconnect.

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Overall Rating: 5 (1 ratings)
infosateng Mon, 10/19/2009 - 05:52

Thanks for the link. I worked with it the other day and came up with this config, but it does not work for me??

voice class custom-cptone testy

dualtone busy

cadence 400 400

dualtone disconnect

cadence 400 400


voice-port 0/3/3

supervisory disconnect dualtone mid-call

supervisory custom-cptone testy

timeouts call-disconnect 5

timeouts wait-release 5


Anyone see what's wrong with my config?



infosateng Mon, 10/19/2009 - 06:13

Do you mean the frequency? The company who makes the device that is sending us the tones told me the following:

Frequency: 425Hz

On duty: 400ms

Off duty: 400ms

With my config I am only trying to match on the on/off cycle of the tones, just in case the Cisco hears the frequency different than what they are sending. I have changed my cadence numbers up and down and it has made no difference. I also tried using this command with no effect:

supervisory disconnect anytone

Shouldn't this at lease close the call?



infosateng Mon, 10/19/2009 - 09:34

Ok, so I have the one system working but I have another router setup identically but the devices connected to the FXO ports are a bit different.

When a call is attempted, but there is no answer, there is an automated message saying the user is unavailable, then just dead air.

The first system (the one that is now working) had the same message but gave tones back after the message.

Is there a way to shut down the port when silence is heard for a long time?



infosateng Mon, 10/19/2009 - 10:59

A call come in from the PSTN to our Gateway router, it is then passed on via Ethernet to another router with the FXO port on it. The FXO port is connected to a phone that calls the subscribers phone number. When the called number is busy the phone gives back a message "subscriber not available" and then just dead air and does not send any disconnect signal.

The system that I have working does everything the same, but actually sends back and audible tone (Freq. 425) that is a disconnect signal.

So is there a way to kill the call on the second system after so many seconds of dead air?



Paolo Bevilacqua Mon, 10/19/2009 - 12:11

No, but that's not an issue, because the caller, after hearing the message will hang up and that's it.

infosateng Mon, 10/19/2009 - 12:18

Well, you are right, if it was a normal caller.

The issue we have is when an auto-dialer calls in, they hear the voice from the message and they don't hangup. But you bring up a good point, maybe if the auto-dialer does not hear any audio returned it will hang up? I hope!

Thanks again for your help.

I think we are just going to upgrade these units to match the ones that do send back a busy tone.



Paolo Bevilacqua Mon, 10/19/2009 - 12:34

It is responsibility of the "auto-dialer" to hangup after message and silence.

If you want to avoid problems like that, use only ISDN or ethernet interface, not analog.


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