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One way vioce communication problem-Voip

I have a problem of only calling from any extension on a PABX to any FXS service equipment and UN ABLE to call from any service equipment connected to an FXS to any extension on the PABX via the FXO.

Although the call could be complete in one way as explained, there is a delay in the FXO to go OFF HOOK when the call is initiated from PABX. As such because of the delay, sometimes the call could not complete.

When calling from the FXS service equipment, the call could not complete. The FXS is going OFF HOOK quiet alright but instead of getting the dial tone from the FXO after dialing a number there is only a SILENCE.

The arrangement is as bellow.

Extension _____ PABX _______ FXO _______ FXS _______ Phone

From PABX Router Router


Calls could be complete from PABX Ext. to Phone, sometimes delays occur between PABX and FXO as explained.


Calls could not complete Phone to PABX Ext. . Silence occurs between FXS and FXO.

How can I go round this problem?


Re: One way vioce communication problem-Voip

Often times complex troubleshooting issues are best addressed in an interactive session with one of our trained technical assistance engineers. While other forum users may be able to help, it’s often difficult to do so for this type of issue.

To utilize the resources at our Technical Assistance Center, please visit and to open a case with one of our TAC engineers, visit

If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

Cisco Employee

Re: One way vioce communication problem-Voip

FXO ports do not provide dial-tone. Perhaps you need to incoming called-number X command under the inbound pots peer along with the direct-inward-dial command. Add these and give it a shot.

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