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sagar.sarker
Beginner

Call disconnect problem for PSTN lines terminated at FXO

Hi,


I have been configuring CCME with 2821 router that are connected with 10 PSTN lines. When i make any call to any of these lines and hang up the connection, the phone continue to ring for sometime may be for 30 secs, then stops. The line i made the call remain busy even though line went disconnected long time back. Can any one give me a suggestion on below issues-


1. how to make the ip phones stop ringing immediately after hanging up the call?

2. how to make the lines free to use immediately after disconnecting the call?


For your convenience, below is the configuration for one of the voice ports-


voice-port 0/2/3
supervisory disconnect dualtone mid-call
supervisory custom-cptone AMC_CPTONE
  echo-cancel coverage 32
timeouts interdigit 3
timeouts call-disconnect 1
timeouts ringing 30
timeouts wait-release 3
timing hookflash-out 50
timing sup-disconnect 250
caller-id enable


Best regards,

Sagar

5 REPLIES 5
Amit Divekar
Cisco Employee

Hello Sagar,

                  Could you please try the following


Under the voice-port

1) try no battery reversal
2) shut
3) no shut


Please let me know if that helps


Please rate if the posts help



Regards,

Amit

Hi Amit,


I already have tried this with no avail.


Rgds,

Sagar

rassoul.ghaznavi
Beginner

Hi Sagar,

Two things,

1- Make sure about Cadence and Frequency from the provider and adjust them.

2- Make sure your dsp chips are working fine:

You can find some tips to test dsp on here:

http://www.net-grp.com/2009/09/30/how-to-test-dsp-chips-on-call-manager-express/

see if all dsp stats are ok.

jijopaul
Beginner

Hi,

When loop-start signaling is used, the FXO interface of a router looks like a phone to the switch, a private branch exchange (PBX), public switched telephone network (PSTN), Key-System, to which it connects. The FXO interface closes the loop in order to indicate off-hook. The switch always provides a battery so there is no disconnect supervision from the switch side. Since a switch expects a phone user, for example, an FXO interface, in order to hang up the phone when the call is terminated on either side, it also expects the FXO port on the router to hang-up. This human intervention is not built into the router. The FXO port expects the switch to tell it when to hang-up, or remove the battery in order to indicate on-hook. Because of this, there is no guarantee that a near-end or far-end FXO port disconnects the call once either end of the call hangs-up.

The most common symptoms of this problem are phones that continue to ring when the caller has cleared, or FXO ports that remain busy after the previous call should have been cleared.

Refer to these documents for workarounds and further background information:

sagar.sarker
Beginner

Hi,


Not quite sure if this can be a solution. I have created trunk groups for FXO ports and configure dial peer against those trunk ports. Now calls are disconnecting properly as soon as we hang up the phone.


Would appreciate if anyone can describe the behavior or the logic behind this. But at least I am happy that the problem is no more.


Best regards,

Sagar

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