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FXS - sending DTMF

I have an ATLAS 550 with the following basic configuration (simplified for brevity):

PSTN (ISDN-PRI) <--> Adtran 550 <--> Octal FXS <--> Fax Server

Our PSTN carrier is configured to require 4-digit unverified account codes when placing outbound calls. We uses this for accounting purposes. After dialing the phone number the carrier plays a go-ahead tone prompting for the account code. Accounts codes are sent subsequently as inband DTMF digits. After reception of the digits the call completes.

The issue is when outdialing from the fax server (or a butt set in testing) to the PSTN from an FXS port the go-ahead tone is not heard nor are the outdialed DTMF digits sent to the carrier. This scenario only happens when using the above configuration.

We also use the ATLAS to terminal multiple PRIs to our PBX in the following basic configuration:

PSTN (ISDN-PRI) <--> Adtran 550 <--> PBX (PRI_ISDN)

PRI to PRI calling works fine using account codes as detailed above.

It appears that the FAX module is not recognizing the answer (tone prompt) sent by the carrier. Is there a setting on the FXS (or PRI-ISDN) module that would open the outbound audio path immediately after dialing?

Any assistance would be appreciated.

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Re: FXS - sending DTMF

Thank you for using the ADTRAN Support Forums.

There shouldn't be any configuration in the ATLAS that will effect your application. What do you hear on the butt set when dialing out on one of the FXS ports? The ATLAS should send out a SETUP message and the Telco should send back a CALL PROCEEDING, to acknowledge the SETUP and confirm it is processing the call, followed by an INBAND AUDIO AVAILABLE which cuts the talk-path through so the "tone prompt" can be played over the talk-path. You would have to monitor the ISDN messages to confirm this. (In the ATLAS under EVENT LOGGING you will have to set the ISDN L2 FORMATTED events to INFO.)

If the ATLAS receives an INBAND AUDIO AVAILABLE message from the Telco, then talk-path is cut through so the caller can hear the audio message being played. If it is working PRI to PRI then it should work PRI to FXS - the principle is the same.

The ATLAS will either play ringback on the FXS port or cut talk-path through to play audio from the carrier (depending on the ISDN message received from the Telco - either ALERTING or INBAND AUDIO).

If you can capture the Event Logs in the ATLAS, that may help.


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Re: FXS - sending DTMF

Thanks for the prompt and detailed response Patrick.

>What do you hear on the butt set when dialing out on one of the FXS ports?


I'll setup logging when our traffic is much lower. Possibly this weekend.