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TA800 with AT&T Syn248

dowop

October 06, 2020 18:10

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Hi,

I'm working on configuring a TA800 for use with an AT&T Syn248 telephone system and have a question regarding a off-hook timeout. 

The TA800 is using Firmware 41.19.0.32.  For the most part it is working great.

My question, when I receive a inbound call, the call correctly goes to the AT&T Syn248 where the AT&T IVR message is presented to the caller.  If the caller terminates the call before the IVR message is complete (selects an extension, etc.) the TA800 stays off-hook for about 60 seconds.

Cannot figure out what could be causing this.  The call log on the TA800 and the SIP provider correctly reflect the call being terminated without delay.

When using the Comcast Digital to Analog box I don't see this issue.

Any thought on how to configure this in the Yeastar?

Thanks in advance!

  

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4 comments

• 0
  
  Larry Neblett October 07, 2020 11:23

  The issue is the form of disconnect signaling and which side ends the call. The TA supports tone disconnect and polarity reversal. So, it really depends on if the call is ended by the  ATT PBX or if the call is ended by the external caller. If the call is ended by the external caller, as you indicated, this is signaled by the ITSP sending a SIP Bye message. 

  The BYE message is then translated by the TA on the analog side such that you should be able to hook up an analog phone to the device and then call it using the SIP provider and once the call is established, hang-up and listen for whatever happens. I suspect a disconnect tone will be sent (to the PBX), but the PBX does not support the method (or polarity reversal). The PBX may want to see an open loop disconnect instead which is when the battery voltage (loop current) is removed from the line for a period of time. The TA apparently does not support this.

  There is no timing adjustment as the disconnect method is absolute in that it tells the other side to disconnect and the other side should, but it depends on what disconnect method the other side supports.

  The device is lacking open loop disconnect, which is what most PSTN, at least in N. America, use in addition to tones. I tend to think the firmware could be modified to support the function, but that is up to Yeastar to determine. I am guessing that when conceived, the device was engineered to be used with an endpoint such as an answering machine, fax or telephone handset. In the case of the answering machine and fax, most do respond to the disconnect tone. In the case of the handset, the local side would either initiate the hang-up, or if the remote side ended the call, the local would her the tone and manually hang-up. 

  Unless you can change the disconnect method and/or perhaps the tone settings at the PBX, I am afraid there is not much you can do with the TA.

  However, there is a device that you may be able to add that might do the trick, but again you need to determine if the disconnect tone is being sent. 

   

  The attached will shed some light on the situation and the possible solution. 

  http://sandman.com/knowledgebase/call-party-control-cpc-troubleshooting

   

• 0
  
  dowop October 07, 2020 12:29

  Good Morning Larry,

  Thank you for the thorough explanation of what could be going on - much appreciated.

  After some testing last night, I'm beginning to believe that there is a possible issue with the TA.  I eliminated the AT&T PBX from the equation and connected an analog phone directly to the TA Port 1.  I set up packet capture and called in from an external number through the SIP provider.  The phone rang, I answered it and then disconnected from the calling phone.  The analog phone went to a fast busy tone and held the port open on the TA.  It never released the port until I hung up the analog phone.  I then analyzed the packet capture and do indeed see the SIP BYE and the TA responding with a Status: 200 but never hung up the phone line.

  I tried toggling the polarity hangup and that didn't help.

  I'll read your posted link shortly.  Could I be on to the issue?

   

• 0
  
  Larry Neblett October 07, 2020 13:39

  Most analog phones do exactly as you have indicated, which is what I indicated - a phone has no detection method as it is the person who would hangup. And, in most cases if left off-hook, it change to the off-hook tone or announcement informing that the receiver needs to be hung-up.

  When the BYE came, the TA then started to send the tone which is in fact the disconnect, The TA then sent the 200OK indicating that it had done so (send the disconnect).

  You have four choices -

  1. See if there is a way to change the disconnect signaling in the PBX (doubtful).

  2, Purchase the CPC signal generator as shown in the article (expensive)

  3. Find an ATA that supports open loop disconnect (CPC)

  4. Submit a feature request to modify the device F/W if possible (doubtful and probably not soon enough for you if they could/would do it.

   

  You can also refer to the following -

  https://support.yeastar.com/hc/en-us/community/posts/360017906074-FXS-port-staying-off-hook-when-remote-call-hangsup

   

   

• 0
  
  dowop October 08, 2020 12:47

  Thanks again Larry Neblett - going to move on and purchase a different ATA.  Too bad because otherwise it is a very capable unit.