Grandstream GXW-4104 - doesn't disconnect PSTN line if caller hangs up

[e23cx]

Hello All,

I've configured Grandstream GXW-4104 on my 3CX, and it works fine. But after some time I realized that if the caller hangs up, the PSTN line on GXW is still connected and it stays connected until the called 3CX extension hangs up.
Usually if the user answers the call, then user hangs up immedeatelly after call enss, but in case the call is transfered to teh voicemail and the caller hangs up, 3CX keeps teh line open until voicemail length reached.
I tested both scenarios:
1. dialing from my cell phone to a 3CX extension. Caller (my cell phone) hangs up, but in 3CX extension I hear "busy tone" from PSTN line and the line keeps connected. Only after 3CX extension hangs up, the line disconnects.
2. dialing from my cell phone to a 3CX extension. 3CX extension hangs up, the line is disconnected immediately.

On GXW-4104 in FXO line settings under "FXO termination" I have also set "Enable Tone Disconnect:" to YES. but this still doesn't help.
And also under "Call Progress Tones" I set "Busy Tone:" frequencies to correct based on TSB E.180 document.

did someone have the same issue before?

 

[leejor]

Most PSTN gateways offer several disconnect methods.

The most reliable is CPC (Calling Party Control), which also goes by other names. This is a very short disconnect of battery, on the phone line, sent by your provider when the phone, on their side, hangs up.

These guys are trying to sell a device, but give a good explanation of CPC...

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

Not all providers offer this however. Check to see if yours does. The next best method, is to detect the disconnect tone, which it sounds as if you are using. This requires that the gateway be set for the specific tone(s) sent by your provider, otherwise it will not work. It also means that they have to send the tones. The third, and least reliable method , is silence detection, which can have a tendency to drop calls, if there is an extended low audio level, such as being put on hold, with very low hold music.

 

[e23cx]

I've already enabled all possible call disconnect options in Grandstream (screenshot below). But none of them works.

the phone provider is in china, which AC Termination Impedance should be Global complex impedance.

 

[leejor]

Since you have current disconnect enabled (CPC), and that's not working, I have to assume they do not offer it. If they are sending a tone, after a time, when the party on their end has gone on-hook, then I also have to assume, that you have (perhaps) not defined the tone correctly.

 

[e23cx]

finally I got correct Busy Tone values from the ISP: ch1-4:f1=450@-11,f2=450@-11,c=38/32;
after this the call is terminated correctly.

 

[leejor]

Glad it worked for you. It is unfortunate that CPC is not offered universally. But then every central office switch, or ATA device, is different.