Disconnect supervision fight with telco

Hi, I’m in need of a little help here. Our asterisk installation works well with the exception of a few minor issues. At issue here is our disconnect supervision. We use a TDM13B and it will only clear our lines with a busydetect. It works, but we are constantly getting VM that is nothing but dial tone, etc… After dutifully reading my documentation, we try hanguponpolarityswitch and still, the lines won’t clear. So, I test our lines with a POTS phone. The phone does not flash when the other party hangs up. So, I call our Telco and tell them that we need disconnect supervision on our lines.

They remote in and tell me that DS was already enabled, but that they manually enabled it on each line. I test again and still no flash on the POTS phone, but I can now hear “clicks” when the line disconnects. I retest with our Asterisk box and still no love. So, I call the Telco back and tell them I’m still having trouble. Their line is that they’ve got it enabled, they’ve done it for lots of other clients without any problems so it must be my switch. Nuts. So, I dug around and found the manual for their T1 interface box that splits our T1 into voice and data. I’m hoping I can call them and tell them exactly what I need enabled on that box for Asterisk to cleanly disconnect the lines on our TDM13B. The box is an Adtran 624 and the sections of the manual I thought might be pertinent were in the FXS section (because FXO ports will use FXS signalling, right?) :

    Specifies the interval of battery removal during a forward disconnect state. Choices are FOLLOW SWITCH
    (default), 500MS, 750MS, 1000MS, and 2000MS. When using ATM mode, there is an additional choice of
    IGNORE SWITCH. If the timer is set to FOLLOW SWITCH, the Total Access 6XX will follow the switch at all
    times; this is normal operation. If a time period has been selected, the Total Access 6XX will remove
    battery for the specified time period OR as long as the switch requests battery removal, whichever is
    longer. For example, if the timer expires but the switch continues to request battery removal, the Total
    Access 6XX will follow the switch and continue to remove battery. For ATM mode, if the timer is set to
    IGNORE SWITCH, the IAD will never remove battery.”

    In Tandem mode, FWD DISC DELAY defines the time battery is actually removed/reversed once the forward
    disconnect is received. Choices are 250 MSEC, 500 MSEC, 750 MSEC, 1 SEC, and 2 SEC. Default is 1 SEC.”

    In Tandem mode, selects whether battery is to be removed or reversed during forward disconnect. Choices
    are REMOVE and REVERSE. Default is REMOVE.”

My thoughts are that it might just be that option 1 needs to be changed as if the unit is set to follow switch, I am willing to bet that the TDM13B will not send any kind of signalling and the battery will never drop. So I thought that forcing 750ms might do the trick since zaptel.h is set to look for 500ms. BUT, I wasn’t sure if I would need to tell them to change option 3 to reverse as well or INSTEAD of changing option 1. Option 2 just looked relevant to me, but I’m not really sure how it differs from 1 so I included it.

Bottom line is that I’m not too sure how much patience they will have when I call them back and I’d really like to have all my ducks in a row. If anyone would like to look at the manual in its entirety, it can be found here:


Thanks very much for the help, I hope I have been thorough enough without being wordy. Thanks very much for the assistance,


    In Tandem mode, selects whether battery is to be removed or reversed during forward disconnect. Choices
    are REMOVE and REVERSE. Default is REMOVE.”

Set this to REVERSE and see what happens