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Thread: PSTN Line gives inaccurate call duration

  1. #1

    Default PSTN Line gives inaccurate call duration

    We have a Quadro 2x

    We are trying to write some software to produce billing reports based on call duration from CDR.

    The problem is that unanswered calls have a duration greater than 0. This occurs only when making calls on the PSTN not via our ITSP.

    It would appear that when making a call via the PSTN line the call duration time is from the moment the call is placed rather than from the moment the call is answered.

    The net effect of this would be that someone would be charged for a call placed that was never answered.

    Is there a PSTN setting that I am overlooking that will rectify this.

    Please advise

  2. #2
    Quadro Architect
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    You are completely right - the outgoing calls through FXO lines are considered as started immediately as soon as the call is done, but not from the moment when it was answered. This is due to the limitation of the analog port signaling. There is no setting to change that, as this is not a configurable behavior, but rather a forced one: we are forced to make that kind of billing because of the natural limitation of the FXO inteface...

    The billing will work correctly on all other outgoing call types, however. If youy make call through ISDN or E1T1 interfaces, ther call duration will be correct (due to the digital signaling used there). The sanme applies to the calls done through ITSP.

    So if you really need correct billing for outgoing calls, you have to use one of those - ISDN, E1T1 or ITSP.

    Best regards,
    David

  3. #3

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    In the older days the way around this type of billing in Australia was via 50hz or 12khz signalling, nowadays it is via polarity reversal for PSTN type services.

    This may be a workable situation for the Epygi but it would be utilisation of old technology that is being phased out.

    Kev

  4. #4
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    Kev, do you know if the "polarity reversal" method is really applied by the telcos in Australia to indicate the billing start/stop?
    I have listened much about this way of "remote side answered" indication to the PBX (polarity is switched by telco when called party answers), but have an impression that most telcos (if any) don't have indication implemented (or maybe it is switched OFF on regular lines going to customers who didn't request that feature to work)...

    Best regards,
    David

  5. #5

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    The polarity reversal method is used in smaller hotel/motels across Australia....

    What it will do is once a call is established reverse the polarity so that when the call is hung up their is a termination of the calls and the call is cleared down. PSTN needs this otherwise you will end up with line lock up.

    I have just rechecked the Telstra website and they are still offering 12khz metering for Motels/Hotels see section 3 of the following document.

    http://www.telstra.com.au/customerte...heroptions.pdf

    This is from http://www.telstra.com.au/customerte...er_service.htm

    Maybe Alloy can follow up with Telstra regarding this or the polarity reversal or as its sometimes called - Reversal on Idle option.

    The polarity reversal is only sent when the establishment of the call is made and in the past it was fairly easy to identify that especially because there are a number of carriers within Australia.

    I hope this helps in your endeavours.

    Kev

  6. #6
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    Thanks, we'll look into this... not sure how important this is now. Looks like these services are disabled by default, thats why we never observed them in practice.

    Best regards,
    David

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