SPA3102 disconnect detection scenarios

Unanswered Question
Feb 28th, 2010

Just wondering if in those scenarios SPA should start disconnect tone  detection and release FXO?

1. PSTN -> FXO[SPA]IP -> IP[SPA]Line1
PSTN drops the call

2. PSTN -> FXO[SPA]Line1
PSTN drops the call


I have this problem too.
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David Harper Sun, 02/28/2010 - 20:28

Yes it should.  IIRC the factory default config for the SPA3102 will identify disconnection of the FXO line based on power denial, batter-reversal, or detection of US disconnect tone.  It is also capable of disconnecting based on long silence on either or both call legs, but this is disabled by default as it can result in spurious disconnections if one party remains silent for too long.

In a lot of cases, the PSTN does not supply either power denial or battery reversal disconnect signalling, and you need to rely on tone detection for disconnection.  This means that the tone configuration generally will need to be modified if you are not located in the US.  Unfortunately, since disconnect tones vary between countries, between telcos in the same country, and sometimes even between telephone exchanges of the same telco, it can be a little hard to get this right sometimes.  Google can often be a big help here, as it is frequently the case that someone has already been through this process for your country or telco.  Failing that, the worst case scenario is that you will need to capture a sample of the disconnect tone in question so we can figure out what frequencies and cadences are being used.



souren1977 Sun, 02/28/2010 - 20:41


Thanks for prompt reply. However I will elaborate more...

Let's take scenarion #2, which is more simple.If the line is dropped by PSTN subscriber and SPA user is still off hook on line 1, then SPA will never detect attempt to disconnect the call, unless line 1 go on hook and I will see

Last PSTN Disconnect Reason:VoIP  Call Ended

You may say that I've misconfigured disconnect tone, but this is not the case, I've captured the line, extracted freq/cad and confirmed it works in other scenario, when line 1 is not involved, just calling from PSTN to IP, then dropping the call from PSTN:

Last PSTN Disconnect Reason:PSTN  Disconnect Tone

So would like to confirm that "by design" if line 1 is still off hook with PSTN, SPA will not attempt to do disconnect.


David Harper Sun, 02/28/2010 - 20:50

Ok, I understand what you were asking now.  Unfortunately I don't know the answer off hand.  I'll ask someone within the product team to have a look at this thread and reply to it.



samsonluk Sun, 02/28/2010 - 22:47

In my case PSTN -> SPA FXO IP -> IP then PSTN drop call and SPA failed to disconnect (PSTN remain off hook), I just checked Last PSTN Disconnect Reason is "VoIP Call Ended" so imply must be a case of Disconnect Tone detection failure.

WESTERNware Wed, 03/03/2010 - 02:54

I have an SPA-3102 too.  I have a landline and a VoIP line coming in on it.  I have found that when a call comes in, the connected phone rings a reasonable number of times, then hands off to the VoIP portion for further instructions.

Whenever the VoIP picks up the line, indeed, whenever the connected phone is answered, there is no disconnect detection at the end of the call.  In short, I can recieve one call, then no more (unless I cold reset my 3102).

I have tried, fruitlessly to remedy this -- does anyone have a quick guide on setting up the 3102 to detect disconnect?



samsonluk Wed, 03/03/2010 - 03:54

I am afraid no quick guide but you have to figure out the correct PSTN Line -> PSTN Disconnect Detection -> Disconnect Tone: parameter for your TelCo disconnect tone.


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