Hangup detect - line quality

I have been deviled by a couple of installs that were using local phone company POTs lines. They get phantom calls because hangup is not being properly detected. The line stays open after the inbound calling party hangs up and eventually a call is generated internally that shows unknown unknown on the caller ID.

The systems in question are Asterisk using digium AEX800 cards that have had their chan_dahdi.conf checked and tweaked by Digium tech support.

The phone company says they see no trouble up to the d-mark.

My question is,…Is there any kind of in-line device that can improve the quality of the signal for better hang up detection.

What form of disconnect supervision is the network operator using? It sounds like the lines are not designed for PABX use.

If they are forced to use domestic lines, rather than PABX ones, what does the network operator do when the calling party clears?

The carrier is Cincinnati Bell in Cincinnati, OH. The signalling is kewlstart.

I don’t really understand your question other than that.

kewlstart is Asterisk terminology. You need to find out what the service provider thinks they are providing.

kewlstart uses a period of no battery on the line for disconnect supervision.

You really need to understand supervision issues if you are going to use POTS lines, in particular if you are going to use ones not designed for PABXes (loop start, which is the other aspect of kewlstart, is not designed for PABXes - real PABX lines generally use earth start).

To see why kewlstart is failing, you will need to enable debugging to such a level that you can see battery states on the line.

I believe Asterisk does have some options for detecting disconnect by looking for tones intended for humans.

voip-info.org/wiki/index.php … upervision

However, note that the advice to use fxo_ks is flawed as it makes assumptions that might not be true of the lines you actually use. Also note that this site often has out of date or wrong information.

Thanks for all your input. I don’t have callprogress=yes. I will see if that makes a difference.

I found this at Asteriskguru.com . What do they mean by “give many false hangups”?

This option is similar to the busydetect option, but will also listen for a ringing tone, congestion tone and will try to detect if the line got answered. It might work for you, but its highly unreliable and will probably give many false hangups.

They mean that, if something that looks similar to the busy tone occurs normally during the call, it will also treat that as a hangup. It is much better to get line state based supervision working properly.