3 Replies Latest reply on Jul 9, 2014 2:28 PM by fluidnets

    TA924e FXS analog not working well over VoIP

    fluidnets New Member



      I have a Telepacific VoIP T1 using a TA924e & all 24 FXS ports for Voice, Fax, etc and all are working well, except Alarm connection over FXS is not stable. I think it is because the alarm call is a continuous session that must have a long quality session for it to work at all! But, my tech measures the voltage on FXS port while on call as 4.5V. If we turn up V to 6V or so, might this help FXS analog port work better?




        • Re: TA924e FXS analog not working well over VoIP
          jayh Hall_of_Fame

          Changing the off-hook voltage probably won't make any difference.  This is a function of the resistance of the alarm gear and the loop current.  Most alarm systems are relatively brief sessions and in general similar settings to fax and modems should work, but disable T.38.


          • G.711 codec only, no G.729
          • No echo cancellation
          • No call waiting
          • no VAD
          • No PLC
          • modem-passthrough


          Changing the impedance settings on the FXS port and reducing the transmit and/or receive levels may help.  This is often a matter of experimentation and trial-and-error.


          Also keep in mind the practical implications on using anything requiring local power for an alarm or safety application.  You want the phone in the elevator to work if the power goes off.  If the UPS powering the Adtran catches fire, you want the fire alarm to work, etc. There are certain cases where a POTS copper loop makes sense and alarm lines often fall into that category.

          • Re: TA924e FXS analog not working well over VoIP
            geo Employee



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